You're reading fiction. Knights on a quest is a Victorian fantasy. Sir Walter Scott based his characters and settings on fantasy. It's very loosely based on historical events and is in no way accurate.
Consider this: a knight was a professional soldier first and foremost. Everything else comes second. It's nice if he is versed in poetry, can sing a song or entertain a noble lady. But his real job is to fight. That is a very grim business. Something like a butcher, but under far more difficult circumstances.
Modern soldiers work on a distance. Real hand to hand combat doesn't happen very often. Medieval knights exclusively worked man to man. Real close up. Had to stick a stiletto through and eye slid, for example. To kill or finish off an enemy. (That't the reason they carried a stiletto or a misericorde.) A 'real' knight didn't do long distance work, with bow and arrow. That was something for peasants.
Those guys aren't exactly feminine types squealing about flower arrangements with the ladies of the court while dressed in colorful tights. A modern comparison might be more of a a Hell's Angel type of personality. In colorful tights, admittedly, as this was the fashion of the day.
What did a knight do when he 'had to go' and was in battle? He simply had to let it go. There and then. There weren't any potty stops. And keep on fighting. His squire had the not so nice job after battle or a tournament to help him undress and clean up his armor. The knight would be very tired, sweaty and covered in feces and urine under the waist. Outside most likely covered with blood, mud and gore from the battle (or the tournament). He probably stank more than a skunk could stand...
That is something you don't read about in Medieval fiction novels. There is a vast difference between reality and what people would like it to be. For example, to protect the poor, innocent and damsels in distress wasn't exactly high on their priority list - if it was there at all.
Did they really march around looking for excuses to fight?
Yes, they did. Or at least, some did. William Marshall made his fortune that way. He definitely wasn't the only one. Doing the tournament circuit was very good business. A tournament rule was that the loser of a battle would have to ransom himself, or buy back his armor. You can get very rich in a hurry that way - or dead broke.