They CAN'T employ any tech like this, for any number of reasons. Some are (but not limited to) -
A: a user may lack internet access, making it impossible to 'register' a game disc in any meaningful fashion.
B: one PS3 console might have to be replaced by another for any number of reasons. Demanding that the user throws away an entire software library and re-purchases it again is totally unreasonable.
C: a person might want to take their games over to a friend's place. There's no reason Sony should want to take any affront to this whatsoever, quite the opposite. If the friend likes the game, it could result in another sale. Therefore, if the games won't work on the friend's system, well, that's a missed sales opportunity.