Why are we playing games?

Zubon at Kill Ten Rats has a nice article about pro-social design.
While the article is good it also scares me in a way as it seems to hint that the reason I play games has been put by the wayside completely. Here's an excerpt:

For example, consider Marks of Triumph in The Lord of the Rings Online™: Shadows of Angmar™. The epic quest chain is a big feature for LotRO, but it was punctuated with instances that demanded full groups. If most of the population had completed them all, how did newer players and alts get through the epics? You asked someone to repeat one. Repeating one was a way to help friends, but you got jack for it. Your friends had to give something up, and you would not meet new people unless someone was a very charitable stranger (or, lucky day, you find a few people who need it, a couple of whom have charitable friends). Game update: repeating one of those instances began to award (once per five days) a Mark of Triumph; accumulate several Marks to barter for various rewards. The rewards were rather nice for when they were released. Pro-social behavior increased.

Ok. very nice game mechanic to make people do something they don't want to. Erm, hold on what is it they don't want to do? Well, play a rather nice grouped instance of a game. You know, have fun playing. Why don't they want to do that? Because there's no reward in it for them. The nice mechanic provides that mechanic.

Now, on the one hand I'm all in favour of mechanics like these, that give a little more incentive, but what bugs me is that the author never once considers people might actually want to redo that instance for the fun of it. Are instances so horrible we really solely do them for the rewards they give? These rewards that ostensibly make us better at playing the game are the goal now, not having fun playing the game. Just the Phat Lootz.

Yes I know, old argument and really not what the article is about. However, it sometimes bugs me the way we're all put on the treadmill of rewards where the joy of game is no longer in having fun anymore.

Worse, its an unspoken accepted fact by now it seems.