why do some people treat me differently when they find out im autistic?

im not rlly sure how to word this but sometimes im rude without meaning to be and so when someone calls me out on it i tend to apologise and mention im autistic so i dont always pick up on social cues but i am working on it etc. but often when i say that or just when people find out i am autistic, they go soft and gentle (im not sure if thats the right way to describe it) and treat me like im a toddler even tho im nearly 18. they say things like 'awww its ok you dont need to worry about that' and it feels so condescending and their whole demeanor changes and suddenly im being treated like i cant do things for myself and i need help with everything and i cant think for myself. (i do need some accommodations for my autism but not a lot, i dont need much support for it). why am i suddenly treated like a baby when people find out im autistic?