They might be used in phones, just not as the CPU/GPU. Think, flash memory controller etc.

I was talking about my laptops -- terrible sorry this wasn't clear! I thought the cafe/home/office example made it clear. Who works all day on their phone?

They aren't for laptops either.

Think about something more like a toaster or a temperature sensor.

Or a pacemaker - something drawing power for a very long time, and where recharging/replacing is literally painful and power failure is deadly.