According to recent estimates from NPD Group, just 12% of tablets sold in the U.S. are cellular models. That's a relatively small percentage, showing that the market has voted largely in favor of Wi-Fi-only models since consumers don't feel the need to constantly have their tablet connected. It also doesn't help that not all tablets are offered with cellular options.

Within this subset of the market, AT&T (T -1.37%) is the leading carrier with 49% market share, while Verizon (VZ -0.68%) Wireless trails with a 42% share. That's 91% of the cellular tablet market occupied by the two largest domestic carriers. Sprint Nextel is far behind with 7%, and T-Mobile has just 1% of the market.

In the video below, Fool contributor Evan Niu, CFA, explains why it's important for carriers to grow cellular tablet sales while pushing shared data plans.