Sometimes when a company performs consistently well, investors become numb to good numbers. Strong results are expected, so when they come in, they don't make major headlines.

That's what has happened with T-Mobile (NASDAQ:TMUS). The company consistently adds at least one million customers each quarter, and it has added more than five million customers each year for the past six years.

The Un-carrier continued that dominance in 2019. It closed the year adding 1.9 million new customers in the fourth quarter, giving it 7 million additions for the year. That's both impressive and ho-hum because the company has been delivering growth on such a consistent basis.

T-Mobile CEO John Legere.

T-Mobile CEO John Legere is stepping down later this year. Image source: T-Mobile.

The merger looms large

T-Mobile plans to merge with Sprint (NYSE:S). That deal would put the company on equal footing with its chief rivals AT&T and Verizon when it comes to subscriber counts. That's important when you consider the level of investment required to build a 5G network.

The merger has passed federal hurdles, gaining approval from the Federal Communications Commission (FCC), but a group of state attorneys general still oppose it. That could scuttle the deal, which would be a blow to T-Mobile, but a blown merger will simply slow the company down, not derail its long-term success.

Outgoing CEO John Legere celebrated the company's success in a press release. His remarks were filled with his usual bravado, but they do lay out why the company will succeed with or without a merger.

"7 million net customers have chosen to join the Un-carrier movement in 2019, and they are choosing T-Mobile because we treat them right, we eliminate their pain points, and we are changing the rules of this industry for customers everywhere," he said.

Treating consumers well is actually a novel concept in the wireless space. That has been a competitive advantage for T-Mobile, and it's one that its rivals will have a hard time copying.

One-time monopolies struggle to change in a way to compete when their industries are opened up to more competition. That has been evident in the cable industry, and it's unlikely that AT&T or Verizon will be able to rapidly (or slowly) become customer-first companies.

A foundation for success

T-Mobile isn't a flash in the pan or a novelty. It's a company that has added more than 1 million new customers for 27 straight quarters. That's nearly seven years of steady, strong growth. Merging with Sprint will super-charge that growth and give the company a bigger base to spread out 5G expenses over.

That would be nice for investors, as it's a sort of shortcut to success. In reality, though, while shortcuts are nice, they are not needed. T-Mobile has shown that, given time, it will eventually catch up to its rivals. The company has built a working business model that sets itself up well for long-term success.

The Un-carrier has built a strong bond with its customers by treating them well. That's a pretty good plan that protects the company from pricing pressure or new, low-cost rivals. That should be enough to keep the company as a growing player in the space, even in the unlikely event the merger gets denied.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.