I think perhaps the ascendance of "analytical" thinking has resulted in the league overlooking the fact that in a single all-or-nothing game, the variance of the three pointer can kill your chances of winning just as easily as it can win you the game. A great team has to be able to switch gears and manufacture good looks closer to the basket when the outside shot isn't falling.
It's easy to look at the math and say three pointers make the most sense and you should try to take 40+ shots from outside every game. But you gotta remember human nature as well. Missing shots when your season in on the line, with the whole nation watching, can perhaps have a snowball effect where each miss makes the next shot less likely to go in as you get tighter and press harder.
Even absolutely fantastic teams can fall victim to this. Look at what happened to Golden State in the 4th quarter of Game 7 in 2016. They couldn't get a three pointer to fall in the same situations that the three had gotten them out of all season long, and they didn't have a good fallback. They just kept chucking.
In a single game, when a dozen possessions or so are all that you have left to save your season, you need to be able to get the most out of each possession. You can't afford to take a big picture, big sample size approach.