In just six years, sports-first streaming-platform fuboTV (NYSE:FUBO) went from zero subscribers to 1 million. Even just over a year ago, at the end of the tech company's second quarter, fuboTV's subscriber base was much smaller than it is today, at just 286,000.

The company's surging subscriber growth is certainly impressive and a good reason for investors to be optimistic about the company's long-term potential. But even this notable figure doesn't fully capture fuboTV's business momentum.

There's an even more promising metric for fuboTV investors to be excited about the future: the company's triple-digit advertising-sales growth. In Q3 specifically, advertising revenue rose 147% year over year.

Here's why investors should care about this metric.

fuboTV displayed on a smart TV.

Image source: fuboTV.

About that skyrocketing advertising revenue

While fuboTV's value proposition clearly resonates with consumers, it's particularly attractive to advertisers. Combine streaming, sports, live television, and technology that lets ads be bought and served programmatically, and you have a recipe for very attractive advertising spots. No wonder fuboTV's third-quarter advertising revenue increased 147% year over year. 

What's really impressive about this advertising-revenue growth is that it's on top of an extremely tough comparison. In the year-ago quarter, advertising revenue increased 153% year over year.

Not only did advertising revenue surge, but advertising revenue per user increased 10% year over year to an impressive $74.54 -- far ahead of the $40.10 of average revenue per user that Roku is generating across its platform over the trailing 12 months. 

All the right catalysts

In fuboTV's third-quarter shareholder letter, management explained the numerous drivers behind its surging advertising sales.

This ongoing momentum is driven by strong subscriber growth and enhanced monetization, as we continue to drive success from industry trends, specifically the rapid adoption of CTV devices by consumers, the migration of sports and entertainment from linear to live TV streaming and the shift of linear ad dollars to CTV.

More importantly, management says it expects these trends to accelerate going forward.

FuboTV management also pointed out a specific catalyst for the near term. After seeing "a large influx" of new subscribers in the last few weeks of September, fuboTV believes it can boost monetization of these users -- particularly those who stick around as long-term subscribers. "This, combined with the continued acceleration of advertiser demand and growth in the overall market, will continue to drive strength in our advertising business," management added.

So why should investors care so much about fuboTV's momentum in advertising sales? It highlights both the company's momentum with consumers and the seemingly insatiable appetite marketers seem to have for fuboTV's platform.

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.