France in the 18th century often didn't seem to press its advantages at the negotiating table. The most notable example came after the War of the Austrian Succession (1744-48), when France gave back the Austrian Netherlands (now Belgium) to Austria even though it had conquered it, and conquering Belgium had been a long-time goal of France's. Apparently this was done because France's Louis XV hoped to avoid overly antagonizing Britain, but if so, the plan failed because the two countries were at war just a few years later. This peace treaty was bitterly resented in France.
In the American Revolutionary War, France conquered several of the Lesser Antilles in the Caribbean, but returned them all except Tobago. Why is not entirely clear. It may be that Louis XVI, like his grandfather, wanted to avoid making Britain thirst for revenge and another war.
Tobago was a fertile sugar-producing island and Senegal was a major slave-trading station, so they did bring some value - though not enough to offset France's enormous expenditures in the war, which eventually fueled the Revolution.
Britain, in contrast, seemed more eager to press its advantages, and after the Seven Years' War it managed to keep almost everything it had conquered. It must be noted though that France was fairly willing to let its North American colonies go, as it was tired of having to repeatedly defend them against their much more populous neighbors, especially when their only major export was furs.