I don't understand why the captain can't play

What does the captain do during the 3 days that is so difficult that a guy couldn't play one match a day? Play the afternoon match both days and the singles match on Sunday. He'd have time to watch the guys in the morning sessions and be able to do whatever the captain does then make the pairings for the afternoon matches and make the match selection for the following day in the evening when he's done playing. While the matches are actually going on, what exactly does he do that makes you think that he can change the course of what is going on in the matches that are currently playing? You think if one of the guys is not playing well that he can go up to him and say, hey, you need to hit the fairways more and stay out of the bunkers around the greens and it miraculously just start happening or give him some swing tips, hey man, you aren't clearing your hips? It's not like he has to make the decision to call the bull pen and send in a guy off the bench during a match as a reliever because he's struggling. For the life of me, I just don't see what the big deal is. The tough part is already done, making the selection of the 6 captains picks and letting the guys who didn't make the team know. Once they are out there playing there really isn't much that he can do to change the outcome.