The curses-based pinentry defaults to using its standard input stream to
display the prompt, but this fails when stdin is a pipe. It does
provide a command-line argument to specify a specific file name, though.
Auto-typing the password, instead of copying it to the clipboard, is
more secure, since any process can read the contents of the clipboard.
It is also significantly more convenient, avoiding the paste step, and
works in situations where pasting isn't possible (such as into a VM
console).