For security, we've moved away from storing plaintext passwords. If users didn't receive their password they should still be able to use the password forgotten/reset link to get it again. Or alternatively, if you wanted to tell them their password you could manually reset it to something else and then tell them.
We don't recommend storing plaintext passwords, but one way to do that would be to add a field "password_plaintext" and write a plugin that updates that field every time a user successfully logs in or a new user account is created.
Hope that helps!