isn't the fun in a game sort of the competitive aspect? i mean it wouldn't be fun if 40k was like youth soccer, everyone wins just for trying, and after we get ice cream. instead, its enjoyable to think "if im playing this army i need to buy this..." "how can i make this kill more people faster?" nobody likes to lose all the time or win all the time (maybe not so many complaints about winning). its fun to be a little cutthroat, just as long as you don't go overboard 
thats why nobody wants to play with furbies any more...
When I first started playing, I would play against only 3 players, Mike (space marines), Chris(necrons) and Derek(orks) the latter two you may never meet but the first is in NY. We were learning basic concepts of 40k and how the mechanics worked. We would tried the most nutso combos we could dig out because it was fun and we were all doing it. So it became apparent that having berserkers (old chain-axes!) were particularly devastating as we the ability to roll combats into each other while bloodletters could be summoned right into combat.... etc. It became stale.
How many times can one stomp on a necron player and have it be fun? Since it was 4th edition at the time, Derek's Orks were pretty terrible so it wasn't much competition. Mike was the only one that could keep stride with all the stuff I would pull. The reason Mike was the only one that could put up a fight was because of the relative power of the codecies.
Derek and Chris don't play 40k any more. Causation != correlation and all that.
Some people only like playing against painted armies. Some people like smashing face constantly. Some people like being fluff maniacs.
It's a mindset thing. I prefer a relatively even fight when I play 40k. If I think my opponent might be gearing up for a fight, I won't disappoint them. The power creep / poor rules hurt balance of the game. Citadel is a modelling company that just so happens to make rules for their models.
