You say that loot is a problem, yes it is. You say that people want cash as fast as possible, once again, true, but we are not talking about money here, we're talking about fun and playstyle.
Unfortunate that professions aren't balanced? Yes. Gamebreaking ? No.
What's gamebreaking is the awful living story stuff so far...
@ Baldur - this ^
if the OP were asking why only Guard mes or war for speed clearing, then this would be an entirely different discussion. but he's asking is there a need as a whole to only play these three professions and the answer is most definitely no.
now you can say that the ultimate goal for everyone in GW2 is to make money and buy precursors and in that case then sure these three professions would be a necessity as its the most efficient way to achieve that ultimate goal.
unfortunately - that is not everyone's ultimate goal with GW2. precursors are for legendaries. i for one have no interest in getting a legendary. not a single one interests me. i play a thief, so the shortbow or daggers are the only thing i would want and well. . .lets just say the shortbow aint my style if you know what i mean and the dagger is ugly. i mean i like the flame blade but hte hilt? is ridiculous.
i think infinite light > bolt
i am actually pretty upset with Dawn and Twilight as they are the same skin with different colors.
anyway, without going on too much of a rant, for someone like me, legendaries arent interesting.