Lol this feature was introduced somewhat recently and the community was overall extremely pleased with it.
Granted, it was implemented more for 1v1 than team games.
But the idea is that it enables players who want to play with a random civilization to do so without being at as much of a disadvantage.
Picking civ obviously gives players a chance to pre-plan their build order and strategy.
No one can do that if everyone is random.
Some of us prefer playing that way.
I will note that I never saw this utilized at all in team games until a month or two ago, and now it feels like roughly 1/3rd of my team games are random.
I’ll only select the option for team games if my teammates also have it toggled on.