Because it would probably be way too easy.
Because who wants to crosstrain like Kobe Bryant?
Or other pro basketballers?
Also why would you want to do the same fitness thing as a celebrity?
There's literally no way to look tough while doing it.
Who needs a core that's ridiculously stable and strong?
Core strength is ¯\_(ツ)_/¯.
Pretty "eh" if you ask me.
You can't even look decently strong while doing it.
It's not a good way to stay in shape while injured.
It can't help you stay flexible and loose for other sports.
You can't just pick up and do it anywhere.
You need a ton of equipment to do any of it.
It doesn't make for a good father-son bonding activity.
It would get in the way of weight training.
And it wouldn't even be challenging.
In fact it would be almost TOO easy.
Newer fitness trends are for young people.
It's not a thing you can do with other dudes.
All you do is lie on a mat.
It's impossible to look cool while doing it.
You can't do anything impressive with it.