The ideal wood block is made from pieces of exterior-grade plywood glued & screwed together to make the desired thickness. The reason is the plies in plywood are criss-crossed so it won't split easily like 2-by lumber. But neither plywood nor lumber is as light and convenient as plastic blocks. With my last 3 big motorhomes, I had plywood blocks for the jack legs and also carried a few 2x10 in case I needed something under one or more wheels.
Big rigs usually don't lack for weight capacity and storage spaces, but B-vans, trailers and smaller motorhomes may not have a lot of either. Sometimes those limitations lead to compromise solutions.