I had a WiFi only original iPad, then cellular (Verizon) iPad2 and iPad3. I have never used the cellular radio on either of the two more recent iPads. Going WiFi only for the Air.
I generally use it either at home or at work, where I've got good WiFi coverage. "On the road" for me usually means in a hotel someplace (where a client may have to pay so I can have WiFi, but I can get it) or at a client site (where I can typically access a guest WiFi network). Plus, my work will give me an LTE hotspot when I need it for travel; if I happen to forget to reserve one, I can tether my iPhone in a pinch. So it's easy to see why I don't need the cellular capability of the iPad.
Of course, this is my use case, and your mileage may vary.
I generally use it either at home or at work, where I've got good WiFi coverage. "On the road" for me usually means in a hotel someplace (where a client may have to pay so I can have WiFi, but I can get it) or at a client site (where I can typically access a guest WiFi network). Plus, my work will give me an LTE hotspot when I need it for travel; if I happen to forget to reserve one, I can tether my iPhone in a pinch. So it's easy to see why I don't need the cellular capability of the iPad.
Of course, this is my use case, and your mileage may vary.