Why are stay-at-home mothers disrespected so much?

i'm a stay at home mom by choice. i worked from age 16 til i had my first daughter at 23, no i didn't work that long but i also have a college degree and still i'd rather be at home raising my children than let someone else (babysitters, family, friends). i've gotten alot of crap for not working but if my husband can support me to be at home with our daughters then so be it... i'm happy with my life and i don't care if other women look at me differently for not going into the work world.