Strange thing though, when you finish that last level, there is nothing left but those professions. Maybe it is something that people didn't think of -- why reroll a character, if you can retain your killer face-eating orc and make him pursue a degree in artistic smithing. There would be a lot of new content, and his (the player's) level would only help to ward off the monsters -- he would finally have time to entangle himself in a proper story-line. No rush or competition, just a journey of discovery.
And thus you unravel the purpose of this entire thread -- creating meaningful time-sinks outside the straightforward "level up and then do end-game at which point sit around bored or leave until new content"
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The issue with being stuck doing nothing is that in themeparks you are limited by how fast the dev team can make a new expansion and then raise the level cap and add new items to craft. In a sandbox with no level cap, item decay and so forth its much easier. If there is no dev defined story you don't have to wait for new chapters. Imagine a George RR Martin style 6 year wait for the next installment of story. Blargh!