Notice, he doesn't specifically say, "Some of you obeyed and the rest of you did not." Instead, he subtly suggests this through his teaching method when he says, "But I want you to know that the head of every man is Christ, the head of every woman is man, and the head of Christ is God." This is Paul's explanation for the matter, and he presents it in this way to engage the less attentive.
You see, someone who is faithful, as they should be, and steadfast, as they should be, this person doesn't need to know the reason for the commands. The steadfast are content with the rule alone, but for the weaker brother, when he understands the reason for the commands, it helps him to keep it in his mind and to comply more eagerly.