Why can't you powergame and roleplay?

[Tormsskull]

The part where close allegiance to the concept presented is just as important as power.

Ah, ok, so when you say concept you're still referring to mechanics. Someone says "I want a guy who is good at Sneak Attacks" and then everyone tries to make the most powerful sneak attacker that they can.

Or someone says "I want a guy who uses a 2-handed weapon" and then everyone tries to make the most powerful 2-handed weapon wielder that they can.

The ongoing theme here is that mechanical power is the goal.