Plastic and steel are common because they're easy to clean reliably. The problem is that the properties that make them easy to clean--smooth, inert--are the same properties that allow pathogens to linger.

Microsurfaces on, e.g., hardwood have properties that sequester and kill pathogens. (https://news.ncsu.edu/2014/09/cutting-boards-food-safety/) However, that can also make them more difficult to clean, particularly in a commercial or industrial setting where the process needs to be low-cost, minimally labor intensive, scaleable, and reliable. Similarly, the surface properties may be difficult to maintain or restore. For example, perhaps oil build up on wood surfaces regularly touched by passers-by reduces or eliminates the antimicrobial qualities, or even make it worse than the alternatives.

That's the rub--how to design (and market) cheap hardware that is easy to maintain while maximizing antiseptic properties during use. We've optimized for the former (cheap, easy, reliable sanitation) but neglected to appreciate that actual cleanliness sucks because typical materials in high-traffic areas go from pristine to cesspools almost immediately and, crucially, stay that way until the next round of cleaning briefly sanitizes the surface.