It's all about Diminishing returns - isn't it time for Rockstar to be moving onto the next game they're cooking? I'm sure that Designers have been working on the next project whilst the Coders and Artists have been putting the finishing touches on the PC conversion.
At the end of the day, it's time for those developers to be making a new game, time is money, and when the additions you are adding don't make more money than they are costing to put in, you have to ask yourself why you're bothering anymore!
Rockstars decision to eschew Multiplayer in favour of a polished, bug free, feature complete single player game is one you'll be seeing a lot more. Frankly I could care less if I NEVER bought another game that came with Deathmatch. Deathmatch is dull, boring and limited. I would like to see new and interesting variants on Teamplay - which I find interesting - especially teamplay that pits groups of humans cooperatively against bots. That's my idea of a good time. Teams of humans working against other Teams is also fun, certainly more fun than playing against the 15 year old script kiddie who skips classes and eating and pees in a bottle by his desk rather than stop playing Quake III.
Eon