I think you’ll probably also find that the “spare” bedroom in many houses ends up getting used for other things—storage, a hobby room, (famously) perhaps an office or second office.
My spare bedroom has a futon couch but I actually use the space for various other things most of the time. Most people may have space that’s underutilized much of the time but that doesn’t mean it’s sealed off until they have an overnight guest or a large dinner part. Things aren’t that binary.
As I pointed out upthread, low frequency is not the same as low probability.
It might not make sense to upfront allocate resources for a low probability event, but it certainly could make sense for a high probability event even if it was low frequency ... like a spare bedroom, or a dining room, or a car with good range.
The probability of using those things are 1 i.e. guaranteed.