Same reason there would never be interest in a movie about Dominique and Gerald Wilkins, the Morris twins, the Plumlee brothers. There's nothing compelling there. There's nothing compelling about the Thompson twins story. They were considered top 10 high school players and they made it, the story about brothers who were always supposed to go to the NBA and did.
Steph and Seth Curry there's something there because they didn't get scholarship offers to major colleges coming out of high school despite having an NBA father and one of them became one of the best players ever but it also makes it far less compelling because they're sons of a really good NBA player.
This shouldn't have to be explained to Huskywarrior but here we are.