I remember wondering the why when I saw the interior of Three Broomsticks years back. Lots of real wood in there as well.
It may be a number of factors that decide its use. It’s very realistic, it will last long enough and it is unlikely that the stains used will ever peel, it is likely that it is actually cheaper requiring less theming than would steel. The only real downside that I can think of is termites and fire.
I ponder decisions such as this all the time.