It's because, they were too busy fixing other fings or implementing them instead of writing a proper cheatprotection.
In Crysis Wars you can't join servers with enabled devmode because you get kicked from punkbuster.
In Crysis 2 there is no Cheatprotection like punkbuster, so they thought:
"We have 2 choices:
1. go with the cheaters (we would have MUCH more of them now if they've chosen this) and allow people to edit CVars & use devmode
2. release the game with disabled CVars & devmode"
They need time to implement proper working protections, and so they can't release a proper cheatprotection in 2 weeks or so

You understand me?
I am fully on Crytek's side and hope they unlock the console, not later than when the modding tools get released.
EDIT:
And oh, I forgot:
In the Leak (yeah, I am one of the baaad guys who has got the leak and I have to admit:
In the leak, with the fully unlocked console, etc. in the multiplayer you could just enable the devmode and then you got invincible...
So my logic is imo right
