Saying there's nothing to spend gil on but using housing as an example is a poor argument. It's the buy and trade of houses that actually made things for players with less gil even have less chance to get the house they wanted in the first place. And since housing itself is a finite feature, there are people who won't give up the house of their dreams short of an act of god where they live (in real life) that forces their hand to give up their house, usually through the demo timer.
A proper gil sink for FFXIV would have to be items or features that can only be bought with gil and have recurring expenses attached to them. That or a system where multiple steps requiring gil only is needed to complete.
