Because Android deals with dozens of different devices with dozens of different manufacturers and their attendant development teams, it's harder to roll out new versions then iOS. Even if one of those devices is Google's own. That device is also manufactured with another partner company.
I would think customers would want them to do it right rather than roll out something too hastily -- as in a half-baked maps app.
Besides, why the impatience? JellyBean is not going to expire anytime soon.
Whether they get KitKat yesterday, today, or two weeks from now is not important to most folks.
--Pat