Housing wasn't popular like it is today. The whole housing system was designed on the spot rather than future-proofing. It was more of a competitive feature "just to have" just like Free companies are a guild feature but they kinda just do nothing with it. It's now a problem but it wasn't at the time. But they did take notice and they did impose limits after this (not sure if that's the same player that influenced them or not).

SE won't demolish that person's fleet of houses because it was bought prior to the policy change. In the future, more wards will be added and possibly instanced housing for dedicated zones (like islands maybe?). FF14 wasn't intended to be as popular as it is today and they certainly didn't expect the housing system to be such a big subculture. I've heard that some people have sold their houses for over $1000USD before. Sure, it's against the ToS but that's how much people want houses.