Hi Lorenzo,
If you set the Optimized profile to Mobile data only, ABS then turns the Wifi ON in 10-15 minutes intervals in order to scan for the networks around. It doesn't scan every time screen is turned ON for the purpose of profile switching. It does so if you have Internet set to Optimized ON, but that's in order for the Wifi to stay ON if there's any Wifi you can connect to.
Cell tower check is a bit more complicated. For one thing, it isn't very accurate. You can see the same tower in quite large radius. You'd still need to scan for Wifis, even though you could do it more often when you know you're "closer" to home and less often when you don't see any of that known towers. The other thing is that from one building, you can see tens of cell towers, depending on how you move around the building. That would be quite complicated for the user to set up and if we were to do it automatically, it could be quite error prone and overall a lot of work for not that many benefits.
Ondra