Why do people make me feel guilty about my parents having money?

I’m not a selfish person but people say I am.
My parents make a lot of money and if I complain about one little thing (as all people will find something to complain about in life) people start calling me ungrateful and selfish.

Can they not see my position from my perspective? Just because they make money does not mean they are magnificent parents!

I can’t help my situation so should I really be made to feel guilty about it?
I donate to homeless shelters and thrift stores. I’m definitely not a selfish, cold hearted person! I would give someone less fortunate my last dollar!

I just don’t understand why people feel that I shouldn’t complain about anything in my life because my parents are “rich”.

What do you think? Are they right? Should I feel guilty that there are people less fortunate than me and yet I still complain?

I mean this is going to sound really stuck up but I feel that if my parents make good money, then we should be allowed to buy things that cost a lot of money without feeling guilty about it. They work for what they earn, they should be able to spend it and we should be able to live happily as an upper middle class family.