Well, think of why talent trees exist. They exist to give people a choice in how their character plays. They make your warrior different from everyone else's. Forcing people to pick certain talents serves to negate the purpose of the talent system.

As far as making it more accessible, that's not necessary. Casual players do not NEED the optimum spec. It just won't make much of a difference to them. For the sake of argument, though, let's say you did dumb it down "to their level." Maybe instead of having individual talents, you just have three specifications. Hooray, now it's more accessible! But where does the dumbing down stop? Now these casual players have to comb the forums to figure out which specification is most effective for each situation. So you remove them, and just have classes. Now they have to comb the forums to figure out which class has the advantage, what's likely to happen in future balance changes, etc. So you combine everyone into a single class. Now they have to decide on gear. . .you get the idea.