I guess my point is that people don't always have wifi. I want to use my laptop on the plane (though some airlines now offer super-exorbitantly-priced wifi, I still refuse to pay for it) or in the back seat of a car.
I should be able to tap away at a document or use a Thunderbird-style "send emails when you next have connectivity" mail client.
My understanding is that the Google apps don't currently offer this.