The same way my ND child had to have adjustments made because their sensory sensitivity made them be completely unable to cope with certain sounds or too many busy colours on classrooms walls.
I hate some smells. Some loud sounds bother me. Same if there are too many things going on. I'm not autistic though, so I have can put them out my head for the most part, the same as you can.
My child had to get a special desk (oh I can practically hear a pp foaming at the mouth after her mentioning special desks) because they literally could not cope with all the stimulation. Adults learn to mask to a certain extent so won't be having meltdowns the same way, and some stimuli reactions may improve - but some don't, and asking for such simple little things to manage them IS them managing them.
You not being able to understand why an autistic person can;t ignore certain things is like a man asking why a woman can't ignore certain things - because you're not them.
If an autistic adult was non verbal and still needed personal care, flapped their hands, rocked, had to do the same thing repeatedly, you wouldn't chastise them for it and call them a baby, would you? (Not you personally, people in general). But because an autistic person is more able, they are trying their hardest to fit in to a world not built for them simply because their brain works differently, they're making it up and should just try harder? The disability is the same, they're just on a different part of the spectrum.
This is why they call it an invisible disability and people are so so cruel and dismissive of it.
My adult child 'looks' normal. Can talk away to you quite the thing. Her whole life and my whole life will always be affected by her autism. She will never live independently. Every future plan I make with my employment, housing etc will have to fit round her until I die.
But people say 'well, she doesn't look autistic. She can do this. You just need to teach her. She just needs to learn'.
I have been so upset reading this thread. I really, really thought in 2025 people were less ignorant (again, not aimed at you personally, you asked a question and I've went off on a tangent! Sorry)
My 20 something year old is living in a world where people have these shitty opinions, then when I'm gone she's going to be stuck with the offspring of ignorant, nasty, selfish people.