Possibly, but how often do you use WiFi on a phone?

Basically whenever I'm at home or a relative's house?

Please note: I didn't say you had to connect to these networks. This happens as a background process unless you do a ritual to shut off location services and actively work to keep it off. Most people do not know/care to do this. And even if it's off in settings, some apps have the permission to temporarily override this (and will ask you once to grant it such permission and then have that permission for the lifetime of the app). And regardless of which app overrides said setting, Google gets a copy of whatever the background scan finds (for all Android phones that have the Play store installed, which is most of them).