It is the reason why playwrights would never distribute full scripts. You would only get your lines and the line before your line. You also wouldn't get a lot of time to study your lines. It was common for someone off stage with the only full script to help actors remember their lines.
Emphasis on "in some cases, these unauthorized copies are the only record of a given play". This already happened with radio/television, and will happen with all sort of digital media as future historians scramble to study the late 20th century and early 21st century's internet culture.