Theater is innately ephemeral and that is one of its most appealing and unique aspects compared to some other art forms.
I like old bootlegs because they are a connection to the past; a way to archive and study the history of an artform that I love. Maybe it's wrong, but I don't want to see shows/scores slip away into the empty void of lost music. I want to preserve the history of the musical.
Personally I'd much rather have an audio than a video of a show. I just want to save scores, and perhaps a few performances like Merman's final Hello, Dolly!, etc.
I do feel bad that the artists aren't getting their full financial due, but the alternative of having these shows lost forever seems worse to me. Lord knows I buy every cast album that I can, but when that avenue fails me, I fall back on the bootleg.
Marie: Don't be in such a hurry about that pretty little chippy in Frisco.
Tony: Eh, she's a no chip!