Well it's also a case of limited resource pools, not a cooldown based system. In other games you have a lot of abilities that are situational because they have cooldowns. The only 'cooldown' in this game for most (all?) abilities is if you have enough resource to use it. Having a ton of extra abilities on your bar wouldn't really accomplish much - you'd still be limited by the same pools. It really is a different system altogether.
Let me try something different.
In the card game Magic the gathering it's a standard rule that a player may have as MANY cards in his deck as he wants. Although the genre is very different the fundamental strategy in how you build your deck/player is very similar. If you have too many cards (too much diversity) in your deck, your actions will have a weak cohesion and the central purpose and build strategy will develop too slowly. The idea is to do more with less; efficiency over time. I just ask that we have the option to choose.
what do you have against options exactly? or rather, tell me what you have against other people having them.