It seems that the moderators don't vote to close off-topic very often. Presumably this is because they don't want to exert (or seem to exert) and undue influence on the site.
I feel like this is a mistake. They should either just close the question, or they should have two types of close powers: "vote to close" and "close right now." Since they don't currently have two types, I'd prefer that they simply close questions they feel should be closed.