Because they don't care, and they don't have to care. The advantaged group always has the option of harming the disadvantaged group, and will rarely be penalized. It doesn't matter if fidgets help people with disabilities; abled people have decided to dislike them. You don't have a right to solve your problems. You're only there to be pleasing to the important people.
Fuck that noise.
Spinners make you feel better? Awesome. Spin that fucker.
Just be aware that some bearings inherently make more noise than others. If it's the noise you find soothing, that may be an issue. But for most people, it's the spin, and there are quiet bearings.