Yes, friendly fire in teams has been the standard of competitive smash. While your town does not need to follow this, having it on certainly adds to a more balanced match. Projectile users such as Rob, Link, Samus, Megaman, etc. would wreak havoc with friendly fire off as they can just shoot away from the frontlines safely without too much harm. With 2v2, I would guess it's not that big of a deal, but when you increase it to 3v3 and 4v4, the projectile users exponentially have a better advantage. If they agree to it, then yes friendly fire on should be the standard for theses kind of matches. It's is not fun at all to just get projectile spammed with little risk.