The main reason to buy a console is accessibility.
You are guaranteed to have every game (made for your console) work on your console.
The controller is comfortable, and has few, easy to memorize, fun to press, buttons.
Multi-player is easily accessible. There is 4 player split-screen, and your online friends are all connected and are not unique for each game.
The second reason to buy a console is that some people prefer to game on their TV.
A lot of this is possible to do with a PC (connect a controller, hook up to a TV, interconnected friends through steam or something) but this is not the default.
My qualm with DLC is that it separates the multiplayer audience. I'd be far more willing to pay for a large 50 dollar expansion-pack than 5 smaller, ten dollar add ons.
This would only break the community into two rather than 6 parts, and I wouldn't need to do so many annoying micro-transactions/ purchasing of stupid XBL points.
These large expansion packs could also be available on disk (like they are for PC).
rat-fish's comments