why do parents think that if they help you out here and there, they can always tell you what to do?

my parents go out out of their way to help me. and i love them. and appreciate everything they do for me and my girls. my dad is always there. My mom is my daughters best nana!

I am a single mom in my 30's, going to school. i pay my bills and provide for my kids. I don't ask for a lot. i don't party, or drink, and try to make wise financial choices. But every time they do something for me, (like buy groceries for me, that i don;t need, but it;s never bad to have more food) that they can tell me what to do. Like we did this for you so Saturday you can come watch the dog for us! well, first off, i didn't ask for crap. second, it's the weekend, the only time i have with my kids and to do home work. So what makes anyone, let alone my parents, the right to tell me what to do?

I am not trying to be rude or inconsiderate, or ungrateful for that matter. When they do need my help, i try to help when i can and do for them what ever they want. It would just be nice once in a while to not have strings attached.

So why do my parents think that they can tell me what to do?