Didn't know they did either. Other than retired athletes at a card show or something similar.
Only have a few myself, but they were signed in person and have sentimental value only.
Among the lesser autographs I have is one from Barry Switzer back when he was head coach of the Oklahoma Sooners, this was the early 1980s. This was when Oklahoma was thumping Nebraska all the time, and so I wasn't enamoured of him.
But once when standing in line behind the coach, he turned and upon glancing at me, asked the person with him who I was. "Oh, that's [franksolich], and he hates your guts."
The guy with him had a roster sheet, and Barry grabbed it, writing, "Hey [franksolich], thanks for being a fan! Good wishes, Barry Switzer."
I kept it and still have it, but my opinion of him didn't change until after I read his autobiography,
Son of a Bootlegger, doing a 180 swinging over to admiration. Barry Switzer was awesome.
In early 1978, I met Lord Mountbatten K.G. in person. People were always asking him for his autograph, but I knew royalty does not sign autographs, so I didn't even bother asking. Which seemed to irk him, and he asked, "Aren't you going to ask me for my autograph?"
Yeah, right. I thanked him, but politely demurred.
Less than a month after that, again in early 1978, Muhammed Ali was on the same flight--this was when private airplanes were rather more rarer than they are now--as I was. Other passengers kept going up front to get his autograph. He finally agreed to walk up and down the aisles and sign them, if people'd let him alone after that.
He came to me, reaching over for a piece of paper I was supposed to have, but didn't. He acted taken aback, at least for a second or two. I thanked him, but pointed out that I admired him a great deal; I admired him enough that I thought he should be left alone in peace and quiet, not bothered. He seemed really stunned, but in a positive way.