Common hazel nuts are used mostly for food (fresh or fried nuts, confectionery products, chocolate industry), but it has also pharmaceutical uses (oils, soaps). It can be also used for horticultural purposes. Some kinds of charcoal are produced from its wood. Nut oils are used for oil paints and some other technical purposes.
Major threats are not reported. Eventually, high numbers of deer, livestock and squirrels may limit regeneration. Conifer planting and the discontinuance of woodland management can reduce its abundance locally. Eastern Filbert Blight (EFB), which is caused by the fungus Anisogramma anomola is fatal to trees in the US but it can be controlled by right management.
2) https://www.etsy.com/ca/listing/93049955/1958-leaves-nuts-and-catkins-of-the
3,4,5) https://commons.wikimedia.org/wiki/Valued_image_set:Corylus_avellana%28Common_Hazel%29