Game balance is a tough thing to get right. While most of the time it's pretty okay, there's a few blips that happen in most games that are hard to forsee a lot of the time.
While I can understand why you'd want to use all tools disposable to you, you must remember that these people do NOT use these tools, because they feel they feel they get too much reward for too little input(Read: Unfair). Say, for example, the COD4 grenade launcher, the input is you aiming at their general vicinity, and the output is instant, unwaveringly, death. While every other loadout weapon in the game requires accurate aiming, you're taking the weapon that means you don't have to put in the input, so you shouldn't deserve the reward.
To blow this up to it's logical extreme, if a game had a 'kill everyone' button (God knows why), it could be the best game in existence (bar the button), but the existence of the button would still be there. Is it fair to use that button when everyone else has unbound the function and forgotten about it? More importantly, is it fun?
I myself have run into this kind of thing before, back in the pre-unlock days of TF2, I was an excellent demoman, but everything kind of felt a bit unfair. I mean it took skill to place and detonate stickies, but really it was unfair that I could just get extra kills because the stickybomb damage was too high. (Since I've not really played demo too much, been more of a soldier man.)
Point is, just because it's in a game doesn't mean it's nessisarily fair, or fun. While there's merit to the 'every resource' in the real world, games are not serious business. You CAN have fun without making others feel cheated.
/Rant.