NBA

The reason midseason tournaments of any kind won't take hold is due to cultural differences.

In Europe & the UK these divisional leagues and tourneys make sense because they evoke the literal thousands of years of bitter struggle and conquest different groups had over each other. London by itself is made of up an amalgamation of different groups who were all trying to conquer each other or fend off being conquered.

So there's an ingrained rivalry between states and cities from way back.

In the United States the culture is of one primary colonizing group (Europe/The White Man), and then one group overthrowing the UK to become the U.S.

It's a culture of "Win the whole thing, and all at once." Which is why we're very championship focused.