They want to know exactly who lives where. They can’t track your exact position all the time, but they can know exactly where you call “home”.
“Why” isn’t particularly relevant. It opens up vast new frontiers to prospective tyrants.
It seems like much more damage culd be done if they just got the database of one of the credit reporting agencies.
“It opens up vast new frontiers to prospective tyrants.”
One thing the GPS database would enable is having a high altitude surveillance drone watch the house.