At any given time, a team or both teams may have a player who don't thaw much or are new and don't understand how.
As pointed out above, auto assign helps keep the teams balanced, keep them even so we are not picking and stacking, and allows the community to grow when you get to play along side different people... the social fun part of why we are here. Auto assign is not perfect and you'll never have a perfect solution when teams can dynamically change but also noted, that if the teams become too unbalanced in the middle of the round, then an admin can move players or a player themselves can decide to change teams before the round ends.
The point it, auto assign works and will not be changed.