Of course, that's all well and good for you, but not everyone that would be a potential XBox One owner has the same kind of stable access to internet you do.
I didn't buy an XBox One, but I have been through two periods of time without internet since 2013. First was when I moved and the tech couldn't make it out to my residence for 3 days after I moved in. Second was when my cable modem died and I had to order another one. I ended up playing Steam games in offline mode, but it would have driven me crazy if I had an XBox One suddenly say to me "welp, guess you can't play any of these games you bought" and would have pissed me off to no end.
And that's just times for myself. There are people out there that live in rural areas that are still connected through dial up, there are people living in countries where internet is a bit harder to come across, there are military folks out god knows where that enjoy playing games in their down time. There are too many reasons to not shut your console down just because of lack of internet that it was crazy they wanted to implement that in the first place.