I doubt it's mess. It's cost. I have Priority Pass, so I see a lot of different clubs. Most of them are about the same for food. Small snacks and treats. Usually things that don't require dishes and bowls.

The biggest exception in my mind is the NW World Club in NRT. A surprisingly tasty and diverse selection of western and eastern food. I've never noticed a mess or smell. However, they do have more staff in those clubs than any of the domestic clubs in the US.

Even food for sale would likely mean extra head count in the clubs.