The only thing that gets me is that EVERYONE hosts popular game servers, to the point where you typically sit with 5 or 6 empty ones most of the time but then NO-ONE hosts any fringe stuff which people might enjoy but never have local servers to play on. I doubt it uses up that much processing power just to throw on another dedicated server, so I don't see the issue of just keeping one up even if people only play on it on the weekends.
Two games that come to mind are Brink and Monday Night Combat.
Not sure if Brink servers are back up but the weekend that it was free on Steam I couldn't find a single local server.