May be a year ago there have some meaning to buy young, fast training players, train them properly and after 3-4 seasons they were getting a good players, but training system was brutal broken and now you can buy every player from list with same success.
After that, two mounts ago, game engine was change and game was turned into roulette. Now you can win or lost with every players in your team, not matter what.
Honesty I don't see the reason to train my players, but habit is second nature. Suppose this is the reason continue playing the game.