Maybe some servers need new wards. On Leviathan, 107 plots are still available in the new wards. 3 or 4 of them are mediums. If someone wanted a house, they'd have gone for the small with 0 bids. For the vast majority of the this server, if you wanted a house, you have one.

Leviathan isn't the most populous server, but it is one of the most active-populated servers. Lesser populated servers should have a surplus of houses by now.