Question: Why was the random button removed from Premade 5v5s?

Just a quick question here. Quite a while ago, the random champion button was removed from ranked games. This decision was clearly a good one. Randoming a champion in Solo Queue can cause enormous issues.

Why, though, was the button removed from premade 5v5 ranked teams as well? Some of the most fun I've ever had in league was on a ranked team that my friends and I made in which everyone would lock in without picking a champ. I see no reason to restrict premade teams. A parallel can be seen in the way in which free week champions are disallowed in solo queue but allowed for ranked 5s.

It doesn't seem like it would be too difficult to alter this for premade teams, so I'm wondering if anyone has insight as to the current situation. Any input from a riot employee would be particularly appreciated.