They don’t have to be wood. I know some people who use electrical cord holders as they’re cheap and easy to chip out.
There are rules for th set up which you should look up, but if I remember correctly it must be a set line which can’t spool, must have a 1 ounce or greater weight, be on bottom, and have less than a six inch leader to the bait.
The big advantage of wood over plastic is it won’t shatter when you accidentally hit it with your chisel when you checking them.