The "clipboard" as it is implemented in many (most?) operating systems today, only exists because it's a legacy idea that hasn't died. If it were freshly invented today, it would never get past even the most lenient privacy review.
Think about the pitch for the feature: "So, we're going to make this in the OS, where the user can highlight anything in any application, invoke a command, and then that thing (which could be a sensitive password, private personal information, or the codes to a nuclear weapon) will instantly become available for all applications on the system to read and do anything with. Uhh... NO THANKS!
Ideally, if an application wants to read from the clipboard, it should explicitly ask the user for permission, or the user should have to specify the exact app he's copy/pasting to. This reduces the clipboard's ease of use, but at least makes it NOT a truck sized privacy hole.