By George, I think you're right... so an SMS is a message without a message!
Personally, I wouldn't have a big prob leaving SMS alone, if it was easier to access my home and office e-mail on my cellphone (in other words, without having to use Verizon's mobile web, which sucks eggs, and has never allowed me to access my e-mail accounts). If cellphones included a simple text-based e-mail client, we'd have the choice of using that or SMS... which would be fine with me.
If you did, though, you'd need to be able to set some serious limitations, mostly to avoid spam on your cellphone, and lengthy messages that providers would try to charge you per-letter.
EDIT: I realize there are downloadable e-mail clients for cellphones... I meant as a standard accessory on all phones.