That clearly isn't what they do it.
They need a mechanism to revoke a license if you sell the disk. The only other ways to do it is to require the disk in the drive to play the game or have some mechanism where the user is expected to revoke their own license before selling the disk.
MS clearly doesn't want to require the disk.
The latter has a number of loop holes that leave purchasers with unusable disks.
They could I guess checkin when ever you start the game, but checking in at some reasonable interval seems less objectionable to me.
yes this is the logical thanks for boiling it down
people want to make this about being evil and anti-consumer but it is mostly the logistics of still having to deal with a damned dirty disc, and logic of digital rights management.
they need to disallow it from being played off your HDD if you sell the disc. they need to be sure someone else isn't playing it same time as you (2 for 1)