In the wikipedia article for the 1945 Prague Uprising implies that there were still a large number of German troops stationed in Czechoslovakia; at least 40,000 of them, including crack SS armored units and even the Luftwaffe! Given that at that date Berlin was about to fall, would 40,000 troops and a Luftwaffe squad not at least made the Soviet attack on Berlin much more bloody and prolong the war for another few days?
There are a number of reasons why the Germans did not pull back for the defense of Berlin. The short answer is that they simply couldn't.
The Wehrmacht and Waffen-SS were still ordered to conduct major offensives even in 1945. The Battle of the Bulge was the last major German offensive in the West, but upon its failure elite units from I and II SS Panzer Corps (which had participated in the Battle of the Bulge) were sent to the East and ordered to conduct another major offensive called Operation Spring Awakening. Spring Awakening took place as far east as Hungary and as late in the war as March 1945. It was the last major German offensive in the East and was a failure. The Soviets had well prepared defenses against the German offensive and had prepared a major offensive of their own. They launched a massive counterattack after Spring Awakening failed.
The German units were overrun while the Soviets raced toward Berlin. Soviet units raced each other to Berlin to claim the distinction of capturing the Nazi capital. The Soviets covered ground quickly: they broke through the last major German defensive line on April 19, started shelling Berlin itself on April 20 (Hitler's birthday), and captured Berlin by May 2. The quick Soviet victory was due not only to their motivation to capture Berlin, but also by the fact that the Soviets had over 1 million troops against only about 100,000 German defenders.
Meanwhile, the surviving German units that had been overrun were low on fuel for what little armor they had left and could not hope to catch the Soviets racing to Berlin. Even if the Wehrmacht had the fuel and armor to retreat back to Berlin in time they were often ordered by Hitler not to retreat at any cost, which often resulted in their encirclement and destruction. These overrun units probably would not have made much difference anyway given the vast Soviet numerical superiority.
The story was largely the same for the Luftwaffe. At the beginning of 1945 the Luftwaffe launched Operation Bodenplatte to support German ground units during the Battle of the Bulge but the operation was a failure resulting in the loss of a large number of aircraft and pilots. By this time the Allied air forces were much stronger than the Luftwaffe, which was suffering from severe shortages in aircraft, fuel, and pilots (and many Luftwaffe fighters were destroyed on the ground). With such severe shortages Luftwaffe personnel were typically assigned to help the Wehrmacht Heer, Waffen-SS, and the Volkssturm in a ground role (operating the feared 88s, for example). Remnants of some Luftwaffe units were still able to fly limited combat missions (including the famous JG 52, which operated in Czechoslovakia) in support of local German ground forces, but they were so short on pilots and aircraft that they had no hope of inflicting serious damage to Soviet air or ground units.
In summary, the best German units were sent far into the east for a final offensive and were overrun. The Soviets had prepared a massive offensive and quickly crushed the German defenders before the overrun German units would have had a chance to fall back to defend Berlin. The Luftwaffe could do little to help due to aircraft and pilot shortages, so Luftwaffe personnel typically supported the defense of Berlin in a ground role.
For further reading on this topic I would suggest:
Panzer Leader by General Heinz Guderian
Men of Steel: I SS Panzer Corps by Michael Reynolds
Sons of the Reich: II SS Panzer Corps by Michael Reynolds
The Blond Knight of Germany: A biography of Erich Hartmann, by Raymond Toliver and Trevor Constable (Erich Hartmann is the most famous member of JG 52 and the book describes his actions at the end of the war)
[Disclaimer: I'm fairly indifferent to WWII history, my history study has been on Native Americans in the NW. I'm basing this on the book The Last Battle by Cornelius Ryan, which seems to use lots of primary sources, including interview with many Germans including Gen. Heinrici, the main defender against the Soviets.]
p. 257: (note the highly sarcastic tone of the passage. Hitler was completely wrong, and this really infuriated Heinrici, who was responsible for the defense against the Soviets and was apparently quite competent).
Even as Zhukov and Koniev began feverishly preparing to hurl thirteen armies with more than a million men at Berlin, Adolf Hitler had another of his famous intuitive flashes. The massing of the Russian armies at Kustrin, directly opposite the capital, was nothing more than a mighty feint, he concluded. The main Soviet offensive would be aimed at Prague in the south - not at Berlin. Only one of Hitler's generals was gifted with the same insight. Colonel General Ferdinand Schorner, now commander of Army Group Center on Heinrici's southern flank, had also seen through the Russian hoax. "My Fuhrer," warned Schoner, "it is written in history. Remember Bismarck's words, 'Whoever holds Prague holds Europe.'" Hitler agreed. The brutal Schorner, a Fuhrer favorite and among the least talented of the German generals, was promptly promoted to Field Marshal. At the same time, Hitler issued a fateful directive. On the night of April 5 he ordered the transfer south of four of Heinrici's veteran panzer units - the very force Heinrici had been depending on to blunt the Russian drive.
and on p. 273, Hitler refused Heinrici's request that the panzer divisions be returned. He thought that the stronger concentration of Soviets were near Saxony and were going to attack Prague.
To paraphrase p. 131:
As far as the Luftwaffe, at that time the German air force had basically ceased to exist. In fact, several thousand Luftwaffe men who were no longer flying were assigned as SOLDIERS to the German armies.
So the Luftwaffe near Prague may not even have been acting as an air force, they may have become infantry!
One reason was that the Nazis originally considered the possibility of making a "last stand" at a "national redoubt" in Southern Germany. The idea was that these mountainous areas might be more defendable than Berlin, located on the northern European plain. Prague, and possibly Vienna might have been eastern "anchors" of such a holding.
In the last days of the war, Goering went south as part of the plan, and Hitler "toyed" with the idea, but ultimately decided to stay in Berlin, where he committed suicide. His appointed successor, Admiral Karl Doenitz, elected to retreat to German naval bases in the northwest, from which he felt most comfortable surrendering. So nothing ever came of the "national redoubt" plan.
Put another way, the issue was not one of moving the Prague troops to Berlin, but rather moving "Berlin" to the Prague troops.