In front of you are two $1 bills. One is fresh from the bank....smooth, crisp, the one you check to make sure that a second one is not stuck to the back it was, so new. The second bill is wrinkled, bent corners, looks as if it has been laundered several times and nearly disintegrated. They are both the same; both are American legal tender, both of the same value, and both may be used for goods or serves around the country and several countries around the world.
Now I ask you, which one do you want? The answer seems obvious because it is...the freshly printed, clean, crisp bill. It is human nature. Given a choice, the clean one always gets selected.
So how do we get Sellers to understand this? By showing them. Prior to listing take them to a couple homes; both neat/clean/A+ on presentation and dirty/cluttered/embarrassed anyone saw my house this way homes. More times than not they get it. They, themselves, would choose the A+ home.