https://accessibility.blog.gov.uk/2016/11/01/results-of-the-...
my recollection from speaking to a blind acquaintance is that it is subsidized by some government agency for personal use, and businesses buying it for blind employees are just stuck with it as an ADA thing.
Of course, there's always software that costs absurd amounts of money for seemingly simple things; IDA comes to mind. I'm not excusing it, but that isn't to say that it doesn't exist.
Their moat is that the addressable market is too small for investors to bother investing in.
The native screen reader built into windows doesn't work well with web pages, so you have to get your own tool (sorry, screen reader) specifically for reading webpages. The browsers all have some extensions for this. So yes, now you have two tools to use - the native screen reader and the browser. And they both are garbage (I've used both while my license for JAWS was pending).
Making software accessible just on Windows is complete bullshit and should be downright illegal.
The reason why accessible users use JAWS is that it works across the entire OS and all the programs you have installed; start menu, PowerPoint, web browser, control panel, Google, etc. etc. The problem with the native accessibility tools is that it fragments the accessibility experience; you have one tool for OS operations, another tool for browser work, another tool for this, etc.
So that being said - it is a waste of time to target the native APIs for accessibility. Your target is JAWS and that's it. In fact, I'd argue that JAWS is better at reading HTML than native apps, so Slack is doing the right thing by moving all their apps to the cross-platform one.