See, here's how you should have started your post, LucasNox:
"So why aren't we able to use this at level 50? WoW allows you to use it at any level and Yoshida apparently says FFXIV ARR uses WoW as a model."
Here's what you did instead:
"But but but think of the children! Or at least the 40 year old woman I know who may or may not want this."
I understand why WoW does it: because you can level a 'twink' character for PVP brackets and lock your exp in that particular bracket. Also, previous content that was under a certain cap (MC/BWL/Naxx at 60, TBC crap at 70, WotLK at 80, etc) could be farmed before reaching the current level cap and you could use transmog on it then.
Also, to extend the duration of a game that has been running a long time. You know transmog. is a a feature that came in 4.3, right? Guess which expansion that came with.
Neither of these problems currently persist in 14.