There is no such thing as "proper use". There is only use or lack of use. The game sets no expectations for what a player does with their house, and the only requirement is that they enter it at least once every 45 days to reset the demo timer.

Does lack of use drive me nuts? Yes, it does. I know a couple of players who have bought houses and then ignored them. I ask them why they have the house if they aren't using it and the response is generally along the lines of "I plan to do something with it some day, just not yet, but at least I'll have one when I'm finally ready". I point out that there are other players who want a house that they would be actively using and can't get one. Their response is that it doesn't change their own wish to own a house and they can't control how SE designs the game so others can't get a house.

In the end the lack of houses is something that SE has to answer for, not other players. Let's direct our attention at SE, not at each other.

Also, lack of decoration does not mean the house is not getting used, especially if it is a FC house. Players buy FC houses solely for the workshop access on a frequent basis. Someone may like to use an empty house as a /gpose studio for getting screenshots of certain animations without distracting objects or scenery in the background. Unless you have camped yourself at their house 24 hours a day, you honestly cannot say whether or not it is getting used (and if you are camping it, why are you so obsessed you've turned yourself into a stalker?).