I find it a little funny that you keep mentioning the game changing hands several times, why, because MS was implementing( and claim to still be brining it) a share program that allowed you to share with up to 10 people. I seriously doubt they did this without developer/publisher feedback.
There are many reasons why a DD only console is not a great choice for gamers or publishers.
1. As stated before, the used market is a big part of the gaming economy.
2. We saw from last-gen live numbers that 10s of millions of gamers never even hooked up their 360/PS3
3. The state of Internet is simply not good enough, especially in the biggest gaming economy, America. Such a large of portion of consumers seemingly have r******d data caps in place.
All these = less sales, less profit, and a potentially devastating effect on console gaming if moved to DD only.
You can eradicate the first point by having a digital used market, or mad steam like sales, but the other two are totally out of publishers and MS's hands.