Just say "Thank you"

I can't help but notice that some people just don't know how to take compliments. I am not a sycophantic type of person, and I only give compliments where they are due. Don't be afraid like I am gonna ask for a big favor after my flattery remarks. Why do people feel so uncomfortable with compliments, or just nice gestures in general? Why do they give me those "yeah right, what do you want?" kind of look after me saying something like "you look great tonight." I don't have any agenda other than expressing what's on my mind. Maybe they just get so accustomed to being treated badly, accustomed to tolerating ill-mannered people that they forget how they are supposed to be treated in the first place.