The modern NHL roster construction is designed to maximize cap space when a significant chunk of the team is still under team control. This allows a front office to prioritize elite talent and not have to give up the overall quality of the roster in the name of keeping a singular player. Take the New York Rangers during the summer of 2015.
The organization was littered with veterans who went through four deep consecutive post season runs. A veteran team is expensive to maintain, and in the salary cap era, pretty much impossible to sustain for more than two or three years.