LigH, your point is well taken and most people, even those who disagree with your position, will stipulate to it (provisionally).
I am going to do you a favor though, and intercept what comes next; the obligatory "But This Isn't Real Life" rebuttal. A few posts after, yet another post would have used reality to discredit any proposed limitations of course. Historically, it goes like this: (A) "There should be restrictions on training", (B) "No there shouldn't because of such and such real life example" (A) "Actually, real life doesn't work like that" (C who agrees with B) "But This Isn't Real Life". This circular logic has dictated the pace of the discussion for the last three pages.
So here's the core of the issue: In addition to not being an accurate model, maxing many unrelated abilities *limits gameplay*.
Here's how and why:
The top of character progression is a character with all abilities maxed
Thus, sense of accomplishment is skewed towards that character progression
Thus, anyone who intends to keep playing will have the same goals and motivation
Thus, in-game characters are extremely similar, meaning they act the same, have [many|all] occupations, and their stats don't denote relative meaning
Thus, characters don't need anyone else since they are equally skilled in everything as all others of their pp/tria level (no niches)
Anecdote. Someone in the game told me to contact them if I needed a mage. A mage, I thought, how quaint. Why would he limit himself like that? I already picked up magic for my Ynnwn since it is easy and useful. Am I wrong? Now I know the reader has not been paying attention for awhile since they are already skimming to formulate their responses. If any of you did make it this far, those of you who are RPers will begin to retort, "None of this is true, because I make crap up about my character that is not really expressed by in-game mechanics". To which the obvious answer is "We're talking about game mechanics, which does not affect your fantasy either way, so those are not germane to the discussion".
Now that I've structured all of these arguments into one post, it makes it really easy to reference it. Anyone who uses one of these tired arguments in the future should be backhanded with a link to this post. We should now be able to go new places or let the discussion die in peace.