There's no perversion involved in it, and if you try to convince yourself that you've never done it, then you're just lying.
Because people have usually turned their inside lights on, it's the perfect time to see their living room decor and how they have the room set up. I've come up with more than one good idea for my own house just by seeing what others have done with theirs. Furniture, pictures, drapery ... you name it. There have been several times when I've seen pieces of furniture or art so striking, that its been all I could do to keep from asking the people where they bought it. But ringing a door bell and telling the person who answers "hey, I was just looking in your window, where did you get that sofa?" can lead to all sorts of awkwardness and getting punched in the eye.
Then there's the other side of the coin. You can instantly feel better about yourself just by looking at the godawful taste some people have when they decorate their homes. There's nothing like spotting a floral chintz couch or a particularly ghastly piece of motel art to boost your spirits.
Admittedly, I've seen several strange things while gazing into peoples houses over the years. One evening I saw a man and a woman having a nasty argument through their front window. Normally, this wouldn't be too unusual, except in this case the couple were standing there screaming and gesturing at each other, completely naked. And this was at 7:00 in the evening.
Another time, I passed a couple in their garage, obviously in some kind of skirmish. The woman was attempting to back her car out of the garage, and the man was pushing against the trunk of the car with all his might, trying to prevent her from leaving. There was no yelling, just a silent battle between the two. I just stood there, transfixed, wondering when the woman was going to floor the car and squash the man flat, but a policeman pulled up and ruined everything.
So, in addition to fashion ideas, you can also see some real human drama on these little excursions.
We recently redid our living room, moving and adding a few things to suit our needs a little better. One of the first things I did after the sun went down was to go outside and see how it looked from the street.
Secretly, I don't think we mind it when people look through our windows.