Google's ToS used to, and may still have, a clause that only allows the geocode API to be used in conjunction with maps, i.e. you can't use the geocode results

Google's ToS used to, and may still have, a clause that only allows the geocode API to be used in conjunction with maps, i.e. you can't use the geocode results for whatever you want, they have to be intended for display on a Google map. I used MapQuest's free tier awhile back which didn't have the map usage restriction but was limited to 5000 queries a day, enough for what I needed but probably no where near enough for many applications.