Every wonder why there aren’t as many open-face sandwiches for sale in your local supermarket. No?…..well, it’s political:

“USDA inspects manufacturers of packaged open-face meat or poultry sandwiches (e.g., those with one slice of bread), but FDA inspects manufacturers of packaged closed-face meat or poultry sandwiches (e.g., those with two slices of bread).” – U.S. Government Accountability
Office, High Risk Series: An Update

The upshot is – by adding one more piece of bread, sandwich manufacturers can sell their product without explicit approval from a government acronym and get inspected every 5 years – rather than daily.