Hericium species are often considered uncommon. Hericium erinaceus is regarded as threatened or endangered some places. It is a legally protected red-list organism in European countries such as England and over a dozen more.
Disappearance of large expanses of intact old-growth forests is often blamed for their rare occurrence but a major contributor is the eagerness of humans to cut down trees inhabited by lion’s mane due to shedding large limbs and their upper portion. This is sometimes done out of a perception that the tree is therefore dangerous but firewood harvesting and fire-safety activity is commonly involved. If wanting to encourage more hericiums in the world, aggressive removal of their hosts should be replaced by leaving the trees standing and respecting what falls to rot into the ground as important habitat, especially when it is substantial in size. The usual pattern is for fruiting to repeat itself until the wood is exhausted. People frequently think the Hericium species to naturally be rarities or limited to expanses of old-growth forests but when their preferred habitats (injured, dying and dead trees) are left alone to decay they can be surprisingly commonly encountered inside of major urban areas.
They are often readily overlooked due to fruiting best in mild but damp periods rather than excessively wet periods that can easily damage the carpophores. Fruiting on standing trees or inside of hollows and on the undersides of large fallen debris can also cause them to be missed even when they are abundantly present in the forest. It is also not uncommon for Hericium erinaceus to fruit much higher on trees than will permit safe recovery. This often also helps them be missed as most foragers are not looking for mushrooms that might be located 20 meters high in a tree. And fewer still will take the risk of climbing a tree to harvest a fungus that eats the tree from the inside out.