Some systems ARE designed to work off of pressure. Depending on the system
designer.
John

If the carbon vanes in a vacuum pump fail, any debris will be blown
overboard. If the pump pressurizes the instruments, the debris will be
blown into the instruments, ruining them.

The Piper PA 31 Navajos for one use a pressure system with a filter between the
pumps and the instruments.

John Dupre'