IIRC it’s because plastic cutting boards can be put into a sanitizing dishwasher with reliable minimum-effort sanitary outcomes, whereas wood cutting boards require more rigorous care to remain sanitary and so the US generally bans their use rather than allowing rigor as an option. In the US, rigor is historically something one can trust food producers to sacrifice first in favor of turnaround time, profits, etc. so it does make sense that they’ve just given up and disallowed it. For possible exceptions, look into bamboo cookware and/or sushi preparation?