Here in Austin, Clear is marketing their wireless full tilt: all the media and even door to door (had two salesmen come by). The pitch is that the service is as good as cable broadband (for the "average household") and available everywhere (home, office, kid's school, on the commute).
No idea if that is true yet, but its easy to see how it could eventually be. Makes sense to band together against a common threat.
So, these three companies are trying to prevent people from switching entirely to Verizon because they already have/are considering Verizon's wireless service. Or something to that effect.
(Note: I'm from the NY Metro area, so I've kept an eye on all these companies offerings the past few years.)
To be clear though - companies like Clear and Sprint aren't just selling 4g wireless devices, they are selling hotspots filling the roll of routers that supplant a home internet connection all together.
When Verizon gets in the game - maybe FIOS for heavy need households, 4g hotspot for a light duty setup?
Just logging your home use isn't as good as capturing nearly all of your traffic, even when mobile, for analysis and sale to marketing companies.