Those actors are all incredibly accomplished and experienced in their trade. A seasoned player of traditional music who has learned thousands of tunes and played in many different situations will be perfectly fine using dots to learn a new tune or two. He or she already knows that dots are far less than bare bones and that their art demands the utmost in flexibility. OK, so take your Shakespeare speech into a class of thirteen-year-olds down the local comprehensive and ask then to read it out. Yeah, you can encourage them and praise them, but on a purely objective level their performances, considered alongside those pros you mentioned, will be stilted crap. That's what you get from learning by rote from a book/dots. Stilted crap. So what do you do? You tell them that the words on the page are useless in themselves as a guide to performance and you take them to hear Gielgud, Olivier and Brando. The real thing, not a thing on a page. The with learning traditional tunes are obvious. You get under the skin of this music by listening to it, preferably in live playing, not by reading squiggles on a page.