It's a lot easier to remember the second half if you know the first half (if it's a password and not a passcode)

Half of the password is randomly generated, the other half is something I add that I can derive easily (think last 5 letters of the website reversed, etc.)

That way if my bitwarden gets compromised, attacker still doesn't have my gmail, bank, etc. logins

It adds a little bit of security while being mega simple