Speechwriters are largely unknown, at least relative to the "performer" -- the same goes for comedy (let's say stand-up comedy since it's differentiated from theater and film in your list), and even film, quite often. On the converse, when you see a performance of "Hamlet", who's better-known? The high school kid bemoaning Horatio, or Shakespeare? I think it's just a convenient shortcut for people to attribute a quote to a performer rather than original author, in cases where the original author may be difficult to discern.
I mean, I can go to imdb.com and find out who wrote the screenplay for "Air Force One", but that still doesn't tell me for sure who originated the line "Get off my plane!" Harrison Ford may have ad-libbed it, or the director may have added it, for all we know.
Thus far I guess our society hasn't found it that necessary to create a culture of strict attribution.
Speechwriters are largely unknown, at least relative to the "performer" -- the same goes for comedy (let's say stand-up comedy since it's differentiated from theater and film in your list), and even film, quite often. On the converse, when you see a performance of "Hamlet", who's better-known? The high school kid bemoaning Horatio, or Shakespeare? I think it's just a convenient shortcut for people to attribute a quote to a performer rather than original author, in cases where the original author may be difficult to discern.
I mean, I can go to imdb.com and find out who wrote the screenplay for "Air Force One", but that still doesn't tell me for sure who originated the line "Get off my plane!" Harrison Ford may have ad-libbed it, or the director may have added it, for all we know.
Thus far I guess our society hasn't found it that necessary to create a culture of strict attribution.