(thinkpiece) autism and sensory issues

disclaimer in case you didnt know: i am autistic myself. no offense is intended, or ever will be intended. 

i wonder why autistic people face at least one sensory issue, like is it a brain wiring thing? is it just how it is? idk but i think its interesting to think about. 

like, the feeling of peach fuzz (the little prickly hairs that start to grow back after you shave) makes me want to tear off my own skin, but other people seem to have no issue feeling it. why does my brain violently hate that feeling so much? and as such, why does seemingly nobody else seem to feel that aversion as strongly as i do? i always end up bunching my clothes up under my arms or on my legs so that i dont risk any accidental contact. 

or loud noises out of my control. that might seem more reasonable to struggle with, but for a long time it wasnt rational. for example, sometimes toilets flushing or the bathroom fan would be too loud for me as a kid, and i hated it. back before i knew what the bathroom fan was, i genuinely thought it was something to just make loud noise so old people could know they havent gone deaf yet. it hurt my ears. however, i love to listen to my music and drown out the rest of the world, and it doesnt bug me as much as uncontrolled sounds do. it probably has to do with my feelings of being in control, and the fact that the stimulus is pleasant to me. 

sometimes physical contact would be a lot out of nowhere, and as a kid i would flinch back. for example, sometimes my mom would just fuss with my hair sometimes out of nowhere, normally in a positive way like twirling it in her fingers and such. i would be startled by this sudden contact and flinch away, and mom would be offended. she knows now, and she understands better, but she sometimes still has moments of "????"

i wanna know why certain sensory issues are a thing, and why theyre mostly prevalent in autistic people. is it an autism-specific thing? or is it just a brain thing that also happens to be a coincidence with autistic people?