Your phone is perfectly capable of making this map on its own. Why does it have to share all that information with the Google mothership?
Apple's phones do the same thing, but don't send your personal location history to Apple. (Though I believe the history isn't a full seven years.)
I've tried a lot of automatic backup solutions like syncthing but have had myriad performance or inconsistency problems over the years.
Its tied to my Google account rather than the physical device, and its not data I need to manually somehow keep consistent across devices because Google does it for me.
It's certainly possible to develop user-centric software with the same functionality and polish, at a grassroots level. The fact that the industry is being dominated by VC money looking for scalable winner-takes-all growth is indicative of the magnitude of what's really at stake.
I sympathize with the plight of those unknowingly being spied upon - I've had enlightening conversations with family members when I show them this very feature they weren't aware of on their Android devices - but it often feels like the demonization of Google treats it like nobody ever volunteers in. Because I definitely wouldn't pay for it, but its a nice service to have.
Apple's phones and computers do this, too. This is not unique to Google. What is unique to Google is that Google uses the information to profile you, while Apple just uses the information to draw a map.
Its something you can probably build off the shelf - log position with durations, draw vectors on Open Street Maps. But Google has already given me the convenience in exchange for my privacy. Its one of the rare times I'm alright with that tradeoff.