I was about to ask that...I remember people saying a lot of worlds used to be empty which is why so many houses got bought out by one person. And of course, now the game is more popular and more people want housing.
I remember 2 years ago shirogane housing on goblin was easy to get cause no one was there...I went to work thinking the 3 mediums i saw would be gone but i came back and they were still there.
I think my issue with multihouse owners isn't that they are multihouse owners but that people are blaming them for the housing shortage when in the past there wasn't a shortage...there was a glut. I mean if I could affored it i would buy 2 houses if i saw a free house and no one was going after it