This is a frequent symptom on websites that consist of more JS than HTML: they often won't even let you scroll the page without a mouse, let alone have UI that's visible to plugins(I never tried it, but I'd bet these same sites would also appear basically empty to screen readers etc.).
https://greasyfork.org/en/scripts/40897-old-reddit-please
Works great in Violentmonkey/Greasemonkey.
That part the cynic in me sees as obvious: easier tracking with the perms that most apps require, so they can command a higher price for any ad impressions.
I think the same is true for a great many apps that could be replaced by a well constructed site or, if offline use is needed, a PWA (the argument of supporting old devices is moot: if your phone is too old to run a well written PWA reasonably then it probably isn't new enough to be well-supported by the related native app either).