Connecting to the home WiFi is the most reliable signal that you are home — more reliable than GPS, which struggles through a roof, and instant rather than a minute later.
Satellite positioning needs a view of the sky. Inside a flat or an office it drifts, arrives late, or does not arrive at all — and in places where the signal is jammed it may never arrive. A network name is either there or it is not.
Connecting is a trigger and so is disconnecting. When I connect to the office WiFi, remind me to book the meeting room, or when I leave the home network, remind me to take the keys.
A saved place can also carry the networks around it, so it is recognised indoors when GPS cannot. Those are stored as hashes — see how that works without recording where you are.