I think the accessibility consultants like this state of affairs: they can threaten more lawsuits and extract more in consulting fees.
I think there is truth in this. A lot of the assistive technology (AT) vendors, also sell consultancy.
Go to the Vispero career pages (who develop JAWS for Windows) and a big chunk of the jobs are remote consultancy roles advising clients on accessibility errors and selling for billable hours.
What makes a web page accessible? Why, it has to work with JAWS, of course!
Vispero makes a lot of money from this; the consultants are all in India, the clients are all in the West, so they can hoover up the difference. I get the impression most AT vendors are extremely cheap, which may explain why it takes decades for them to improve things
It's way way simpler than, say, var hoisting in JavaScript.
Not be able to aria-label anything and have the screen reader say ok I take that in priority seems badly thought out.
Also - screenreaders could have a setting to read aria-label on divs and then read the content if the user wanted it. If the user determined the labels on divs were inadequate, they would flip this setting, if they decided this seems to be working well they would just go with what the site does.