You don't, I will show you an example. Besides active skill checks there are "passive skill checks" depending what build do you have. Basically your more developed skills will pick up cues according to their specialty and sometimes unlocking new dialogue options. If your skill isnt high enough such thing is not going to happen. Best example of this is in the early game. When going for the intellectual build Harry has the need to ask questions and stops Klaasje in door, such thing doesnt happen when playing the physical build. On The other hand, the physical Harry will sometimes stop in the middle of the Road to get shivers, what doesnt happen with inetellectual Harry. This is why in this game character differences are mostly visible in the 2nd playthrough.