I'm not against other people choosing to play with power levels, but I think it's wrong to assume that people looking for casual, narrative, or introductory games aren't looking to improve or care about the result of the game. Everybody cares at some level and wants to do better next time. If they don't want to go through the few extra minutes it takes to make a list with points, that doesn't tell me they aren't competitive at some level and care about winning. It just tells me they don't want to spend the time. Which could be because they're in a hurry, or want an excuse if they happen to lose, or they're lazy, or any number of other reasons.
I'm not at all assuming the points are balanced. All I'm saying is that power levels introduce more variance than is already present elsewhere in the game - due to points, or codices, or whether a player went first or second, or stole the initiative, etc. - and I think that's unnecessary and undesirable.
Your last example misses the point. I'm taking issue with the fact that it's impossible to tell whether a points discrepancy due to power levels is significant or not. I don't like that. In light of that uncertainty, I want to err on the side of caution and assume that there is a difference, whereas it seems like you'd prefer to err on the side of ignoring it completely.