It's interesting to resurrect this old thread to compare experiences then & now. Over the past several years I've found, in the US, that when a hotel advertises "2 queens", it regularly is 2 queens. In fact, rooms advertised with "2 doubles" are often also 2 queens. Of course, some hotels really do have double beds -- and advertise them as such.

As for why provide 2 doubles instead of 2 queens, the answer is simple economics. A 2-double layout takes less space than 2 queens, so the rooms can be slightly smaller. And, of course, the beds are cheaper. The difference may seem minor to a consumer buying one bed every 10 years, but to a franchise operator furnishing 100s of beds per property it adds up.