[digitallis42]

Wood is porous and unable to be fully sanitized, as well as absorbing and giving back off everything from soaps and sanitizers to food flavors. Example: chop a few onions on a wood cutting board. Clean and dry. Then the next day wet your cutting board and give it a sniff. The onion is still there.

It also has trouble with repeated washing cycles as a material.

There's some evidence that biologically, wood fibers will dessicate and shred bacterias, and there's the historical anecdotal evidence of wood cutting boards having been used throughout history, but those anecdotes aren't enough for commercial kitchen operation where food needs to be able to be given to all comers, including infirm, allergic or immunocompromised.