I collect some. For modern era I prefer the mfg certified and issued cards. I mean, where else can you get a genuine sig of a HOFer for $10-$20? Great value for the collector IMO.
I also collect sigs I get in person.
I have a few vintage sigs of people who've done something I admire, like several of the 506th PIR (Band of Brothers) soldiers from WWII.
And I have several sigs of my cousin in various formats:
1951 Topps Ringside card, contract and TLS referencing autographing Topps Ringside cards:
Poster, secretarially signed:
Autographed photo: