Why hold conferences in a resort town?
I cannot talk about general customs, but for whatever it’s worth, a major conference in my field is held in a ski resort, off-season. This has two advantages:


This is what the resort does to survive during the warm seasons. Therefore I presume that it may be a relatively cheap option.
Except for hiking, there is nothing to do there. With conferences held in cities, it often happens that attendants take some time off to do some sightseeing or similar. Here, getting to the next (touristically boring) city requires you to rent a car and takes one hour. Therefore, the conference gets more attention.