Agreed. 4G coverage is still in a swiss cheese state. It's been getting much better in my area, but I still don't rely solely on my 4G modem when I'm travelling in the area.
They'll only piss off users when they can't get a connection on the road, ultimately losing those customers. If they focus only on 3G/4G mobile devices, they'd likely have more interest and more long term success. This is simply going to fail.