Personally, I use GPSLogger from FDroid on a 15 minute ping interval and then load the files into Location Map Viewer (also FDroid) for my own location tracking. Disabled Google awhile ago.
I've used my location history to remember names of places I went to over a year ago, addresses I was given and expected to write down but forgot, confirm for myself I actually went and did something that I couldn't recall fully...
It's nice to have a sort of diary sometimes. My only practical application has been to sometimes check which times I arrive to and leave from work when I need to report my hours.
Looks like most of the existing replies captured my same use cases!
There have also been a couple of times where my wife and I disagreed about what we did on X day and it's kind of nice to see who is right 😂
I think I also just like the raw data. I also keep spreadsheets of my utility bills over time, for example, because it's weirdly fun to look back and see or compare.
One thing I'd really love is a self-hosted all-day heart rate tracker, but have yet to stumble on such a thing.
4G masts can triangulate your location quite well based on signal strength and which post you're currently connected to so unless people are planning on removing their sim the government will always have decently accurate localization.