Firstly, for me, it's time.
When I'm in the mood to decorate my house, I would spend all my (already limited) time in-game, across several consecutive days (or weeks) just doing that and nothing else. Especially so when working on custom made things that requires a lot of floating and glitching. Usually during my long holidays off from work. I'm the type of person who commits hard to a project until it's completely done.
Second, if I'm satisfied with what I made, why change it? I've already done my thorough research/housing tour before I commit to my housing project. So I normally don't have the need to make adjustments so often. I'm completely happy to look at my hardwork for a couple of years until there's a bundle of new housing items I'd like to play with.
Third, I'm still waiting for Highland partitions and pillars. *Rolls eyes at SE*