Why would someone want android with crappy apps comparing to linux on the old laptop?
Running apps that require a phone and are not available for Linux, without putting them on your actual smartphone (if any)
Much better security. Sandboxing and app isolation actually works on Android.
Familiarity
App consistency
Upstream app availability and release cycle
Security.
Running apps that require a phone and are not available for Linux, without putting them on your actual smartphone (if any)