Why are calculators one of the only consumer devices with solar panels?

This is actually an interesting question. I think it comes down to two things:

1) Frequency of use

2) Overall power requirement

Calculators are kind of an ideal use for solar panels because people generally only use them for a minute or two at a time and often won't touch them for days. And on top of that, modern calculators use so little power it's frankly ridiculous. We're talking a couple hundred microwatts during use. In comparison, I have trouble thinking of devices with equivalent usage and power characteristics - most devices we use intermittently have pretty high power requirements while in use, especially when you consider that indoor lighting is awful for generating solar energy.

Depends on what kind of consumer you are. People with animals to care for and contain are quite likely to have a solar powered electric fence charger. The cheap "yard lights" are ubiquitous where there are yards.

Note that most "solar panels" in calculators are fake. They have a small battery inside. https://www.youtube.com/watch?v=uLTDuGhqE2w and https://tedium.co/2017/08/09/calculators-fake-solar-charging...

Some luxury cars have solar panels embedded on the roof that can run the fans when the car is in the sun so it is not so hot inside when you get back.

I thought about bolting my own solar panel onto the roof of my car and diverting power to the fan but you would need some kind of transfer switch and the electrical system isn't partitioned to make it easy.

The short answer is that it takes large panels to generate any significant amount of power, larger than would fit on a most consumer devices.