They did sell out, they were acquired by Life360 a while ago.
edit: I don't think Google would have had much to gain by acquiring Tile, the actual technology is very simple, their moat was just the fact that they had the largest install base of tracking apps on Android. Google could, and did, just rug-pull them by pushing their own network out to every Android device with Play Services (so nearly all of them).
The only thing Tile really has going for it now is that their trackers can be used with both Android and iOS simultaneously, if you have devices in both ecosystems.
edit: I don't think Google would have had much to gain by acquiring Tile, the actual technology is very simple, their moat was just the fact that they had the largest install base of tracking apps on Android. Google could, and did, just rug-pull them by pushing their own network out to every Android device with Play Services (so nearly all of them).
The only thing Tile really has going for it now is that their trackers can be used with both Android and iOS simultaneously, if you have devices in both ecosystems.