I’ve been collecting stamps for nearly 40 years now and I’ve found a lot of them advertised as used when in fact they are not used, they are simply cancelled. Unfortunately, a number of countries issue stamps in huge quantities that are cancelled during the printing process and have never actually been on an envelope. While this does make these stamps available globally, it also allows less-than-reputable dealers to sell these as used. Many new collectors do not realize this; I can remember when I first started collecting wondering why I was getting all of these cancelled stamps that still had their gum. It didn’t take long to find out that these stamps are printed by the millions and are essentially worthless.
It’s mostly a case of buyer-beware, as many dealers don’t bother mentioning whether the stamps are actually used for postage or CTO. Next time you go to buy a few used Hungary stamps, keep in mind that they probably never saw the inside of a post office nor the face of an envelope but were created specifically for sale to collectors.