Because it just feels like a big house right now. There should be more exhibits, displays and glass cases which have things in them related to the lore, maybe some easter eggs would be cool like a golden apple in one display case.
It also feels a bit too homey and convenient for Mr. Peterson. The completely normal bathroom should be replaced with a dirty restroom area to make it seem like it was actually an old Museum people visited, with a homemade shower cobbled together by Mr. Peterson as a replacement for the bathtub. For the bedroom the normal bed should be replaced with a matress on the floor.