Nowadays, most people use password managers (hopefully). However, there are still some passwords that you need to memorize, like master password (for a password manager), phone lock, wifi password, etc.
Security wise, can passphrase reach the strength of a good password without getting so long that it defeats the purpose of even using it?
Very similar heuristic here, insofar as when to use passphrases and how long.
LUKS and Bitlocker volumes get 8 words, computer logins usually get 4 words (potentially more depending on frequency/criticality of system).
Smartcards and mobile devices do have numeric pins due to frequency of use and relative difficulty in copying those for offline attacks.
Websites that are filled in w/ password manager get passwords get the random symbol-laden strings that ‘meet requirements’