Apple's the only streaming service that offers only original content. If Apple wanted to be Netflix or Disney, Apple would buy Netflix or Disney. Or any number of other media companies. The company has had good chances to acquire both Apple and Disney more than once if it wanted to but apparently being another massive catalog entertainment distributor is not in Apple's plans. Apple has been buying talent and screen projects, not content libraries, and you can argue whether the company is achieving it's goal but its stated mission is "Quality, not quantity."
Apple doesn't need ST to be a huge money maker. Apple has been dropping billions on content creation and now it's going after live sports to round out its appeal. If Apple does get ST it will be a drop in Apple's revenue bucket. What Apple needs is the halo effect of the NFL to shine light on AppleTV+ content and AppleTV hardware, so I'm betting ST will be packaged as friendly to consumers as the NFL will let Apple get away with.
The NFL app is available on Google TV, AppleTV, Fire TV, PlayStation, Roku and XBOX.
https://www.nfl.com/apps/ctv