They actually do, surprisingly.

Lots of people got tricked on their iPhones after installing ransomware apps on them from the app store.

They couldn't figure out how to exit the app (you had to open the shutdown dialog via long press on power) and went on to pay after getting a scary warning/full screen hijack

Been a while since I read about this though, not sure how frequently it happens currently

The ability to freely run software has its risks, no doubt. But switching to what are effectively terminals centrally managed by big corporations sounds quite dystopian to me.