I did a bunch of testing and research on the shot and touch tendencies a few years ago. For shot distribution, the shot and touch tendencies are related to the percentage of plays called in your coach settings and also the play discipline tendencies for the players. The touch tendency doesn't dictate the amount of plays called for the players (it's for freelance offense outside of set plays). Who the plays are called for is based on the type of offense being run, the focal point in your coach settings, the player ratings, the player's play types and the playbook. If you want to spread the ball around, lower the percentage of plays called by the offense and then the shot & touch tendencies have more impact when the team is basically freelancing on offense. If you run a high percentage of plays though, the stars will generally get the plays called for them.
Be sure to check the player's play types and the playbook too. I was working on a custom roster once and couldn't get the SF to get many shots. Then I looked in the team's playbook and noticed they had no type of plays that were the kind assigned to the player...so there were no available plays to call for him, oops, lol.
Also, the touch tendency is different by position. You'll notice that a lot of PGs have lower touch tendencies (not 90+)...and that's because they bring the ball up the court and initiate the offense. High scoring SGs and SFs will have higher touch tendencies to make sure the ball gets to them when it's being passed around outside of a set play instead of it always going back to the PG. You can also impact shot distribution with the Iso and Play Discipline settings. If you want guys to take more shots, bump up their Iso tendencies and bump down their Play Discipline tendencies....and vice-versa if you want them to shoot less.