Any good player will say: cap only when strictly necessary.
Anyone else should say: cap mostly, since we can't tell when it is necessary and when not. Instead they just say: cap.
As for capping because then you can grind faster with more xp/minute. Seriously, get a real job. If you can't play for fun, and if you can't relax for 2 minutes, why are you playing computer games?
Furthermore, it doesn't hurt to be friendly to your team mates. Yesterday I gave a red player his first Radley-Walters, because (apart from initial blatant kill-stealing), he did spot base when needed without suicide yolo'ing in. Same goes to thank you team when they give you a win.
When you lose it's always: "stupid team, stupid players, whine, whine, whine". Despite that those teams allow you to get epic damage/credits/medals.
When you finally get a good team that wins the battle for you, it is "let's screw them over, totally, and steal all their damage/credits/fun". Or is sitting in a painted white circle really that much fun in tomato land? Or just convenient because it allow for more time to lick windows?