If you've spent your entire hockey career in the minors, it's still more professional hockey than most people get to play.
What motivation is required to play a long hockey career in the minors? Is it a love of hockey so vast that it overwhelms the discomfort of year after year on the bus? Is it because the player has a higher goal of a coaching position, and wants to maximize playing time for extra credibility? Is it expedience, because the player doesn't have a different career, and needs to earn money while learning a new trade?
An ESPN article from 2007 posits that around 5% of junior hockey and NCAA players go on to become players in the NHL, and a hockey agency page has slightly different, but also low, numbers.