I think people train jump shot because they can see it more directly than passing. When a player scores, they attribute it to better jump shot. They don't see that passing (now 18 on transfer list), driving (71 on TL), and jump range (42 on TL) also contribute to better shooting. Also, when JS is trained, players' salary increases more rapidly than with passing. This gives the impression that a player is improving faster when training JS. Because managers look at the salary when buying players on the TL, JS increases the value of a player (salary) faster than passing, player sells for more $.
I am also surprised that people don't train free throws (69 on TL) more. For bad players I can understand this, but what I have found is that even the players on national teams are often bad free throw shooters.
For me personally, passing is definitely not useless. As I said, it contributes to better shots as well as to decrease turnovers, and I prefer balanced players to one-dimensional players.