Very interesting news, with Fan Duel Network going bankrupt, the bucks are putting all games on free over the air TV rather than what the brewers did.
https://www.nba.com/bucks/news/milwaukee-bucks-to-return-to-full-season-over-the-air-television-for-first-time-in-31-years
My guess is that NBA didn't have the infrastructure in place to make it easy for NBA teams to create their own app / network. This was probably the best the bucks could do. When the Brewers decided to do it, many teams already did, so there was a roadmap.