I think everyone would prefer attacker. That's why it isn't a choice.
Attacker allows you to play at your pace. Defender forces you to play at someone else's pace. With this game having such strong grind mechanics, being able to choose the pace that suits the grind you are on, is always preferable. If they let you queue for a team, the slowest would always get defender and would always feel frustrated.
If you play in a community server, you will get attacker and defender every other round. You won't randomly be defender twice in a row or anything like that. Like clockwork. And you will play with the same people. And you will have a known map rotation and won't randomly play the same map over and over.
If you play matchmake servers, it will be random and you will only average the same attack and defender ratio over a long enough period of time.