The reason we do concede is because of the 1-3-1 system we play. We basically have 1 D man. The players will swap about but essentially you only have 1 player on the blue line. This creates outlets at both posts for a pass and a 1 timer, you get the keeper working side to to side and also make it hard for the opposition to set their box PK because the zones are more spread out.
It's clearly a system that works as our PP is the best. But the reason we do concede is we are relying on 1 man for D cover. The puck skips over his stick, which happens, you're toast. The D man has to pivot and create his speed whilst the forward on the PK already has his speed and is away. Or, a turnover in the corner and you give up a 2 on 1.
One of the biggest reasons though, is the exact opposite thing people moan about - shooting too much on the PP. All the groans around the rink and the shouting of shoot does us no good. A good PK will give the point man nothing to shoot at other than bodies, fans all scream shoot, player shoots, the shot is blocked and possession given up creating a turnover on the blueline. It's usually the same people screaming shoot who moan when we give up the odd man rush on the PP because of a blocked shot. I don't think people realise how little there is to shoot from the blue line.