I don't like conflict over "trivial" things so it is almost always easier to give in on pretty much anything that doesn't have a certain amount of emotional significance.

Some of it is trying to be a "good person" by letting other people have what they want, but a significant chunk of it is simply the pragmatism of a child from a large family who learned that being "flexible" was often more pleasant than actually getting into conflict, even when it means not getting what you want.