It's just hobby projects with larger scope.

I can see from a lot of replies the "cool" threshold is undefined, but here goes:

For myself it let me finish a project I started a year ago for measuring how much home energy efficiency upgrades will reduce my AC usage. I bought a pile of Raspberry Pi Picos and turned them mostly into temperature reading devices, but also one that can detect when my AC turns on.

So I can record how often my AC runs and I can record the temperature at various points around the house, which lets me compare like-for-like before-and-after.

The easy but unrealistic way to accomplish what I want is to use Python. It gives me access to a file system, a shell, and all sorts of other niceties. But I wanted to run these on two AA batteries and based upon my measurements they would last about 2 weeks. I tested using C instead and they should last 4 months. That's long enough for my use case. There's enough flash storage for that time period too.

However this means I need to write all the utilities for configuring the Picos myself. There's all sorts of annoying things such as having to set the clock (picos lose it anytime they lose power), having to write directly to flash memory (no operating system), having to write a utility for exporting that data from flash memory, and so on.

And AI coding let me burn through a pile of code I knew how to write but didn't care to spend my weekends doing so.

The pattern is the same for my friends who are software devs. And yeah, you're probably never going to see any of it, but that's not why they're making it, they don't want the maintenance burden.