The British comedian Spike Milligan once surprised a fan by refusing to sign an autograph. He lectured something like: “You’re just asking me because you recognized me. If you were a REAL fan, you would have written to me!”
Indeed, most fans do that. Thanks to the Internet, most every celebrity address is known. Some websites charge a fee for supplying home, agent and manager addresses, and some FANMAIL forums "share" that info free. They post their “successes” or “failures.” And give tips (sample form letters) on how to write a letter without really trying. ("Put favorite film HERE...now say you are a big fan...") Julie Newmar is almost always listed as a “success." See the above. Address redacted (oh, like it wouldn't take you 30 seconds go Google it for yourself!)
Some collectors love quantity over quality. They don't like spending money on photos. They prefer to get 3x5 or playing cards signed. Postage is just one stamp to and from. They can keep the cards in a few neat boxes, and pridefully say, “Yep, I got her. Got him…” and flip through and show it off. Here's someone who has decks and decks of signatures. Did this guy have the wit to pretend he chose the 7 of clubs in honor of "Seven Brides for Seven Brothers?" That IS Julie's real signature of course.
Yes, the forums mention a disappointing RTS (“return to sender”), worry over a "possible secretarial," or let others know if the star sends a form letter stating a price charged for a signature.
Many stars, who were fans themselves, are good sports, or feel it's a good business move. They know what a thrill it can be to get an autograph, even by mail. “Wow, the star took a moment for ME…ME, a nobody in Nowhere Town. I’m SOMEBODY after all!”
Some stars, and some friends and parents of autograph hounds say “Get a life.” But many believe autograph collecting is a nice hobby, and it rewards both parties. Everyone likes to get some kind of validation. The stars who sign, rather than stick in a form letter with an excuse? Well, as Soupy Sales once told me, regarding fans, “It takes just as much time to be nice as to be nasty.”