Alright, then I guess I'm talking about those players who don't lead.

FWIW, I would not lead out with 55 on that flop. It would blow up the pot so any flush and straight draw will draw against you. With a check/raise on the flop (or the turn), you will definetely knock people out. I think very strong hands like Q9 or 55 require pot manipulation to prevent drawouts.