I think a huge cause of the issue (and something I think which should be included) is the fact that you will LOSE certain 'rare' items if you demolish/lose an estate. You can't remove them or they perish. I realize this was done to keep a constant 'flow' of new housing items being created, but it actually causes people to unnecessarily hold onto houses they don't need. By this I mean to say... If I am going to take a long break from the game, I think I would be more likely to willingly relinquish my house if I was able to keep *EVERYTHING* I put into it (except for the full price of money that was put into the plot itself, which I know would be returned as only a small fraction of the original cost). By the way... this is why I'm really hesitant to boot inactives from my FC... because I don't want them to lose their unique items in their personal room even if most are returned to them from an NPC.
Please correct me if I'm wrong about this, as I'm not 100% sure if you can hold onto plots via the 'free login campaigns' they frequently offer... but if you can reset the timer on your house being autodemolished using the free login campaign, then there really is no need for people to hold onto their subscriptions if they are in the boat of... "Well, I don't know if I want to come back, but I don't want to play right now... and I don't want to lose my house because I might come back..." There are plots near me that I have been watching for months and they never go on sale despite never seeing the person who owns the plot around. The character is level 50 and doesn't seem to have done anything with Heavensward. But, the plot is still there... either because that character is an alt or he is using the free login campaign to keep his house. I understand the timer for a plot being autodemolished has been put on hold right now, but this house has been here forever.
All of that said, I don't have a huge desire to have a personal house. I love my FC's house. We worked very hard for it and I stayed up ALL NIGHT prior to the 2.3 patch to make sure we got the plot we wanted -- because I knew that's what needed to be done. If I wanted a personal house, I know I would have to do the same. But, I do find it a little odd that people are allowed to have as many personal houses as they have alts. It seems excessive, especially since there are people who just don't have the option to stay up all night and log in as soon as the patch goes live.