Its a cheap attempt to block 2nd hand games (I don't buy them personally) but publishers make money off them now with online/season passes + normal DLC, so they don't need to block them. It would also cost a HUGE amount of people their jobs worldwide as retail game sellers would take a huge hit. Never mind my internet going down, what happens if XBL goes down?
Yeah, Gamestop makes about half their income from used game sales. It would pretty much ruin them if it became routine to block used games.