You can map a ton of inputs to them or use them for mouse control or more precise stick/dpad control, for a couple examples. I would never buy another handheld without them.

I used them to dismiss the EA middleware bullshit, and Cities Skyline.

They're essential for Factorio, the factory must grow!

As an alternative to thumbsticks for shooters and such. My understanding is when you get used to them they're great for that. I was never able to get used to them on the OG steam controller.