Fan letters will always be thing. I imagine the madly popular actors do hand offs to an assistant (if they have one) after reading. There was a popular younger theatre actor (popular in an Instagram way, but not wealthy enough for an assistant) who got many letters who said his mother would reply with signed photos and Playbills if a SASE was included.
I think most actors will read and many will reply if a SASE is included. If not then yes most things surely get tossed. I think it is very easy to become jaded and toss everything. However I think truly grounded people read and respond if/when they have time.
I have written letters to actors at theatres. I only wrote when I feel very moved to, so that makes a difference. I’m not an autograph hound. Therefore I have received handwritten correspondence from people like Jane Fonda, Charles Busch, Estelle Parsons and Bernadette Peters. One might easily think people of their age and status would be the type to toss, but clearly not the case.
I think actors are very sensitive people and appreciate correspondence. I think they read it all and will respond if it feels meaningful. I think they will respond to requests if a SASE is enclosed. I’ve often received photos or Playbills long after a show closed with kind notes and apologies.
Actors are very good and earnest people for the most part.
"The sexual energy between the mother and son really concerns me!"-random woman behind me at Next to Normal
"I want to meet him after and bang him!"-random woman who exposed her breasts at Rock of Ages, referring to James Carpinello