You don't want to be running away from mobs or even other players and have to stop to do a 0.5 sec cast.
It completely negates the point of having escape artist on your bar.
I know they introduced the 0.5 cast time at one point in Vanilla, but it was soon reversed back to an instant cast.
Even if you up the cooldown to 2 minutes, I'm sure most alliance gnomes would prefer this to the current state of the racial.
Out of interest does any other racial have a cast time?