I guess I would say that your post pre-supposes 3v3 is biased towards long range play, but some of the best players (Lumi etc) are rushers through and through. I think what you really mean is that people play too passively in Trials, probably because they are not playing with people who support them well as a team. If someone doesn't rush with you, respond to your calls and movement it's easier to default to a fairly static style of play, of which our only choice is snipers.