Leveling doesn't really matter that much. I think it makes the biggest difference in WvWvW, but outside of that my level is not something I thought about much. I took on content five levels higher than me, and at 80, content 20 levels lower than me can still put me on my toes.
They could have removed levels, but I think people would have complained about that. There's already people struggling with the concept of seeing unexplored areas just to see the areas and content, and not for any escalating reward system. You take away levels and they're entirely lost.
No one would have complained if they had a decent system in store. ArenaNet proberly just didn't have a good idea how to structure GW2's core concepts into something playable. So they slapped a level system on it. And it's not doing the game any favors.