If you have enough disposable income and aren't planning on leaving home, it's not unreasonable for your parents to expect you to help with home expenses. It wouldn't be fair for you to be living it up while your parents work and struggle to make ends meet and pay the home expenses. If I were a parent having to say no to purchasing things I want, but my adult child living at home had tons of disposable income for online shopping, I'd have a lot of questions too. It's a very different question to if my child was going to school or trying to find a job but unemployed. And given that you reference only your mother, if she's been raising you on her own, without your dad's help, that goes double.

I let my adult kids live with me rent free, but they still have to contribute to expenses around the house in some way. I don’t mean contribute in just the financial aspect either, since expenses also cover the younger kids as well. If you have the extra income and can afford to have numerous packages delivered every week, contributing is something I would also do as well.