FT is not trained much because you would probably need a whole season to change a 10%-guy into a 70% shooter, that would probably be a difference of 20 points scored more - if you invest the same amount of time in another area you will get much better results and output.
i think this change wouldn't need a half season 20%, is most likely a low 2 in this skill a medicore free throw shooter your target would be something betwen 5 and 6 which are 6-8 trainings. And is it not just one player who scores you twenty points more. I think free throw training especially in the low area is extremly valuable, and i look for free throws when i buy player and i train it from time to time.
maybe you would gain 1-2 points more each game with Jumpshots, but when i train free thows i don't had to watch minutes(which could be worth a win this week) or i could rescue a week where my minutes are destroyed. I don't have to pay extra salarys for it.
And yes the players looks weird, and it would make sense out of a realistic view that it get trained with the JS training, but i wouldn't like the change in the training system.