You assume that they can just choose where to place all of their stats. If rolling in order, or with say swapping only one pair of stats, both very common ways of rolling, that can't happen.
True. I just don't know anybody who plays that way personally (and I would not want to). I would assume though that most people are still going to play to the strengths of the points you have. You will still have a high score somewhere and a low score somewhere else, it can't be avoided.
The end result is the same ... if you have a high int you're probably going to play a wizard. You may be an abnormally strong wizard, but a wizard nonetheless.
If that's what you want to play I don't care, it's just my cup of tea. Stats are about the last thing I think of when I come up with a character concept.