You seem to be confusing the capability with the desirability. You talk about Intel, yet the surface is Intel and has lte. But it is rather irrelevant
Most people couldnt care about an always on device. They already have a phone for that, and for the majority of people's internet needs (essentially social media, maps, email etc) a phone is more than sufficient.
There just isn't a demand for yet another monthly bill for something they already have, and are happy with. Notice how the demand for lte in the surface is a minority demand? Everyone else seems fine with tethering. It makes little business sense to design a product for a minority market, especially when you are not the strongest player in the market to start with. The last thing MS want is a few hundred million Sat gathering dust in a warehouse only to become "obsolete" 12 months later.
And btw, there is more to the world than AT&T. They are not going to design a product because of one carriers shortcomings.
Supply and demand. Very simple. No demand, which there really isn't, then no supply.