The market you refer to is dominated by Facebook, Netflix, YouTube, Spotify and maybe the Google Docs/MS Office apps. None of those require a pressure-sensitive screen and largely look and work the same way on mobile as on tablet.

Some iPad apps like Procreate and Affinity Publisher are designed for the pen, but considering that iPads sell in the tens of millions, I'd wager they make up a pretty small portion of the buying public.

Yeah, virtually every app in the Play Store "may not be optimized for tablets". That disclaimer has become superfluous.