I've had to do the reverse... building an accessible application meeting specification requirements because it's used by government bodies. On the flip side, the core functionality of the application (reviewing scanned documents) requires a sighted person to use it.

It really does and should be determined by the specific use case. Yes, most sites should be and many are pretty accessible by default. Using Axe, Wave, Lighthouse and other tools is easy enough and should absolutely be done as part of a web application's development. That doesn't mean that everyone who doesn't do it is someone who should be ostracized and cancelled by reactionary mobs.