This doesn't really make sense in my opinion..
people who have never played the game before in their lives will try the demo and will not be able to make subs, hear commenary, or see any of the other fine presentation tidbits.. so what's the point of a demo? 2k shouldn't be trying to convince their existing fanbase to buy the game, the hardcore people will already buy it, newcomers are the ones that need a good demo.
2k fans have been buying the game for years and will continue to do so for a long time regardless if there is a demo or not, so they least you can do as a company is reward your fanbase for years of dedication by giving them a good product that resembles the real game without giving too much away..
The demos they release are a slap in the face to 2k fans who spend their hard earned money on the game, play it the entire year, and then keep up to date with the lack of news up until October.
I think their sales could go even higher if new people who tried the demo out before buying the game (eg. past Live players who still need a reason to convert over - I've met a TONNE of those in real life - even recently).. so I don't think this is some great 'marketing tactic' on their end with the bare bones release..