Also because many apps won't run on rooted phones. Funny how I can't use my bank's app but can do everything in the browser.

I get the security concern in that case, tbf, but not when it's some entertainment app.

Rooting with Magisk usually isn't enough to trigger SafetyNet failures (which is what most apps use to detect "rooting", among other things). I've been running rooted on my OnePlus 6 since day one without any app ever complaining, including google pay. Custom ROMs will fail SafetyNet typically, but there are ways around it if you want to keep hacking.

For entertainment apps it's mostly about thinking they're preventing piracy.