When done properly, wood charring actually strengthens the wood by drawing out moisture. Charred wood is also more fire-resistant, repels insects and doesn't rot.

Of course all this can be achieved differently but charring usually lasts much longer than other surface treatments.

It used to be common in Japan (yakisugi) but I assume this must have been common throughout the world.

My neighbors large barn in the gold country of California has support pillars under the floor that were treated by charing. Built around 1890 and they are still in good shape.

Structurally modifying wood can be done even better than fire treatment, hence the mention of polymer enhanced wood. (And yes, biopolymers work for this.)