Listening experience at audio shows?

I don't understand why the lsitening experience at large audio shows should be as bad as audiophile convention says? I know that at last year's RAMF there were some very nice sounding rooms, and other rooms that appeared to have the same physical properties which sounded very poor. At major shows like CES, THE Show in Newport Beach, RAMF and others the rooms are the same year after year. Furthermore, even if they weren't the room dimensions are available to manufacturers months in advance, as are (usually) power supply limitations, etc. Given that in today's high-end environment large shows are an incredibly important way to get your product good press and word-of-mouth, why should the sound at shows be much less than the best a manufacturer has to offer (given the specific components chosen)?

I think rooms are usually assigned weeks if not months in advance