Because mail is one of the more anonymous physical ways to interact with someone. Try buying Bitcoin anonymously. Most suggestions have you walking into a bank

Because mail is one of the more anonymous physical ways to interact with someone. Try buying Bitcoin anonymously. Most suggestions have you walking into a bank (highly monitored), or meeting a stranger (easy to be monitored, perhaps even collect a DNA sample, plus could follow you around). Whereas if you can buy stamps anonymously then discreetly drop a package of in an unmonitored mailbox, you're doing fairly well on the anonymity. (Assuming you're using untraceable cash, didn't leave fingerprints, hair, writing style, printer fingerprint, etc.) The best they get is a day + one point of physical presence. Edit: Making it so severe is that the apparently preferred way to get stamps is the machines that print out uniquely marked stamps. Last time I tried all this, I had to go out of my way to find non-serialed stamps that I could pay for with cash.