I used to be a teacher and I now work in a community venue so have had a lot of young people "pass through my hands".
I've always been happy to provide references for them. Before the advent of email, requests often came in the post with a SAE enclosed. Occasionally I still get these but mostly I'm asked by email these days.
However, over the last year or so an increasing number of email requests have asked me to provide a "hard copy" through the mail as well as by email. So I'm expected to provide an envelope and provide a stamp. It doesn't cost much, obviously, but I think it's a cheek.
I get a few requests from a particular agency and last time I responded I said I'd provide a hard copy as soon as they sent me a SAE. A week later I was asked where the hard copy was and I replied by asking where the SAE was.
I don't want to blight people's job chances so, normally, I just do it but I do think they are taking the piss.