It is a love of stamps that takes the collecting impulse that is found in many of us and transforms the person into an ardent philatelist. The collector reads all he can about the hobby and, in the typical trajectory, goes from a more general type of collecting to specializing. The philatelic experience involves searching (dealers stocks, Ebay, the internet, philatelic auctions) in the hopes of finding items that are just right for your collection within the structure that you have used to define your collection, (US Fancy Cancels, German Pneumatic Post or whatever).
Counterintuitively, the very needs and skills that make collecting such a pleasurable experience tend to mitigate against turning your hobby into your profession. Collectors spend enjoyable hours searching for material that is just right for their collections. Dealers who duplicate that process for acquiring stock find that their inventory is too sparse and too specialized. The great pleasure in philately is finding and owning the perfect object. How difficult it is for new dealers, who still have the collector in them,to realize that dealers sell their favorites. New dealers learn that if something is in stock too long it is because you have loved it too well, priced it too high, or put in stock something that is too arcane. Many collectors have the dream of eventually becoming stamp dealers.
They confuse the joys of a hobby with the obligations of an occupation. Some dealers have both but most collectors who migrate into professional philately soon find that their interest in their collection wanes.