From Impossible Visits on youtube:
Except in the case of birches and pines, many branches, limbs, and tree trunks used in structures have been stripped of their covering. It seems likely that this is done in order to retard the rotting process, to make the elements of the structures, and thus the structures themselves, dry out quickly and last much longer. (Very commonly, too, you will find that the branches of the trunks and large limbs have all been snapped off—a deliberate act, not the result of any natural process of decay.) A second reason may be that bare wood tends to show up better in the forest when seen against a backdrop of ordinary trees. Finally, Sasquatch likely eat bark, which is rich in vitamins, minerals, and medicinal properties.