Others, like Stadium, Eleven and FloSports, project bright futures for their well-funded start-ups as they hope to become even fractionally as profitable as ESPN. Leagues can also opt to stream directly on social media platforms like Twitch and Twitter.

“It is the greatest time to be a sports fan in the history of the world,” said Burke Magnus, the ESPN executive in charge of programming. No matter how small or unpopular a league or team is, their games are probably streaming to fans somewhere, he said.

To be sure, even with an energetic promotional campaign, streaming services and the niche sports they show face plenty of significant challenges before they become a viable alternative to broadcast or cable television.

Most important, they need more exposure and more eyeballs. A relatively small amount of people know these sports and services exist. The number of subscribers to the services is a fraction of the 607,000 daily viewers ESPN averaged last quarter or the 87 million homes who receive the network. Far more people would stumble across Karate Combat on ESPN than stream it on karate.com.

Streaming services also have yet to figure out a way to take advantage of the economics of bundling. Pay television distributors pay nearly $8 each month for each subscriber who receives ESPN — and more than a dollar each for the NFL Network and FS1, as well as other regional sports networks, even though a small percentage of their customers watch these channels. Streaming services only receive revenue from customers who actively choose to subscribe or watch.

No sports streaming service has nearly the portfolio of rights of even a second-tier cable sports channel — acquiring those rights would take billions of dollars they do not have. With the recent proliferation of digital sports streaming services, it is possible that many, perhaps even the majority, of the services and the sports they show will fail.