I used to work for a company that did this. The amount of location data out there and how easily it is available is mind boggling. And turning off GPS location on your mobile phone doesn't save you. You can get location data from telecoms directly though it is coarser. If you have a mobile phone on you, you connect to a cell tower, and boom, your location is known to a few hundred feet. This is sometimes preferred because you can fake your GPS data but this comes from the cell towers so no way to fake it. If you repeatedly visit the same places, which most people do, with some ML models so you can localize it further down.

Every app that asks for location data sells it. That includes every single weather app. In some cases, it is a bigger revenue stream than the ads they show.