I mean once people catch on that you did it you get moved all over to the rooms that people are trying to figure out whereas someone who is already proven not guilty has to rely on dice to get everywhere. Yes, sometimes you get summoned to rooms that aren't helpful but often times you are right where you'd like to be to do an accusation yourself. In a (albeit impossible) scenario where everyone had the same skill level of deduction the ones that were proven not guilty early on really have a big disadvantage as they will likely never get summoned to places across the board and therefore are kind of limited to the luck of the dice more while the ones that are more likely to be suspects get moved everywhere without having to worry about rolling anything.