The Softest Hardwood

Because hardness is an important factor and hardness.
The softest hardwood. Classifying wood as either a hardwood or softwood comes down to its physical structure and makeup and so it is overly simple to think of hardwoods as being hard and durable compared to soft and workable softwoods. Although classified as a hardwood alder is one of the softest of all hardwoods and is more commonly referred to as a semi hardwood. First it is virtually unobtainable and not commercially available outside of its natural range in central south america. The hardest commercially available hardwood is hickory and it is five times harder than aspen one of the soft hardwoods.
A hardwood named quipo cavanillesia platanifolia is commonly reported as the softest known wood with an alleged janka hardness of 22 lb f 98 n. On a hardness scale alder ranks just above pine and poplar. Other soft hardwoods. Similarly wood from the yew tree which is one of the toughest woods and is harder than most types of oak is classified as softwood.
However the wood is omitted from this list for two main reasons. For example balsa wood is known as one of the softest and least dense types of wood yet it is categorized as hardwood.