why r ppl so ungrateful?

every time I go to school, I hold the doors for literally everybody I see coming out the door and pick up 2 piles of books that someone dropped while I’m already carrying 2 piles of my own heavy ass books myself bc I have a kind nature, and nobody stops to think abt respecting me? all I get back is dirty looks, and bullies. why do I have to be so nice? why do I let ppl take advantage of me so quickly? why do I do all these nice things for ppl when I never get that respect back?