The numbers do the talking.

Verizon (VZ - Get Report) this week said revenue in the fourth quarter from its wireless services business fell 4.9%. AT&T (T - Get Report) reported a 0.7% decline in wireless sales for the same period.

Meanwhile, Comcast's (CMCSA - Get Report) cable TV business generated a 7.1% increase in revenue, due in large part to the success of its decision to invest heavily in the rollout of its X1 set-top box, widely viewed as the pay-TV industry's best. In addition, sales at NBCUniversal jumped 10.5%.

Besides showing why AT&T CEO Randall Stephenson badly wants to acquire Time Warner (TWX) , these results also demonstrate why Comcast CEO Brian Roberts has long been reluctant to jump head-first into the wireless business.

In recent years, Roberts has had to fend off questions and criticism that the company founded by his late father, Ralph Roberts, hadn't acquired a wireless carrier. For more than a year, speculation has spiked that Comcast might buy T-Mobile US  (TMUS - Get Report) or even Sprint (S - Get Report) . Yet neither came to pass either because Comcast couldn't do a deal or chose not to.

Back in September, Roberts broke the news of Comcast's wireless plans at the Goldman Sachs Communacopia media conference in New York, explaining that it would involve a combination of cellular and wireless spectrum that would use Verizon's network along with millions of the cable company's Wi-Fi hotspots in public spaces and peoples' homes.

Comcast's unique wireless service is the result in part of a 2012 agreement with Verizon that allows it to resell the carrier's wireless services. The agreement was signed as part of a deal in which a consortium of cable companies led by Comcast sold a slew of U.S. spectrum licenses to Verizon for $3.6 billion.

In an investor conference call on Thursday, for a quarter in which Comcast once again exceeded analysts' earnings expectations, Roberts said that while the company plans to enter the wireless business in the second half of the year, the form of that business is still taking shape.

The focus, however, is clearer. Comcast is getting into wireless services as a means of protecting its core businesses: internet and cable TV to the home. In the industry, that's known as lower churn. It's the same reason Netflix (NFLX - Get Report) is producing so much content: to retain customers as much as attract new ones.

Though Roberts was circumspect about describing how the service will work, he did hint that this isn't going to be your incumbent carrier's service.

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"I believe that we'll find out, but we believe, and we're hoping, that it's an end-stage strategy and that it's sustainable," he said. "The goal of the business is to have better bundling with some of our customers who want to save some of their bill, and take a bundle, and have lower churn. And if you can achieve that, and we'll see, the economics really work. And that's the goal."

In effect, Comcast appears to be building a wireless business built around owned and borrowed spectrum, thereby creating an operation that is less that of a typical mobile services provider than a collection of roaming agreements, media analyst Craig Moffett of MoffettNathanson said. 

"Whatever Comcast decides to do, we suspect they will take their time," Moffett said in an investor note on Thursday. "And why wouldn't they? Cable assets would seem to be in a sweet spot; they are advantaged infrastructure in an advantaged industry structure in a regime that suddenly likes infrastructure."

"Why rush into an industry that is less attractive on virtually every dimension?" Moffett said in reference to the earlier results this week from Verizon and AT&T. 

Revenue in Verizon's digital media group, which includes AOL, fell 4.9% to $532 million year over year, though the figure did represent an increase of 10% from the third quarter. But weaker-than-expected wireless revenue was blamed for Verizon missing analysts' earnings per share forecasts by 3 cents and forcing CEO Lowell McAdam to say that it's unlikely the company's wireless business will grow again until 2018.

Meanwhile, Comcast seems to be poised to get the better of its 2012 deal with Verizon and of wireless as a business. 

"Stay tuned, and we'll clarify things," Roberts said. "We have a good relationship [with Verizon], we believe, and we're excited to get it launched, and we'll learn a lot as we go."