Better sandboxing. If one of the programs you apt-get is hacked through supply chain compromise or something, it has full access to all the goodies in your user profile. There are distros that attempt to implement sandboxing but in those distros your browser can't really be jailed properly. Qubes has tighter isolation than android does, but is slower and too much of a hassle for your typical employee or relative.

Android is pretty slick overall and the user experience is simpler and more familiar to people than Windows or Linux (even if they're an iPhone user). You'd be surprised how many people don't really use PCs.

Would be interesting for x86-based tablets/convertibles, like for instance an old Lenovo X1. I tried using these with Linux with various different distributions, including PostmarketOS, and it was not a good experience.

Running apps that require a phone and are not available for Linux, without putting them on your actual smartphone (if any)

Familiarity

App consistency

Upstream app availability and release cycle

Security.

Games is one use case. I play the iOS version of Balatro on my Mac.

Much better security. Sandboxing and app isolation actually works on Android.

I wouldn’t want to run Linux or windows on my phone lol.