Philatelists want several things in an area in which they decide to specialize. They want availability. It is no fun to collect a country or sub specialty where there is little material available and the game is all search and no find. They want affordability. Unless you are Midas (and he lived in the pre-stamp period) constantly coming up against wallet bashing numbers when you find an item you need soon gets stale. And they want high production values-attractive well produced stamps by a responsible post office. Netherlands philately combines all of these factors. Their stamps are well designed and handsomely printed. The issuing policy of The Netherlands has always been conservative and as one of the major commercial and most educated nations of the world their stamps have been well used and retained by the Dutch resulting an active dealer corps with available stocks. There are few expensive rarities and the country is completable by people of even modest philatelic means. There are numerous interesting (and not particularly pricey) sub specialties including compound perfs, design subtypes on the Postage Dues and cancellations that make for interesting sidelights if you should tire of the main stamps. And, of course there are the Colonies.