2-factor authentication (2FA) is encouraged in order to reduce the risk of an account being compromised since the attacker has to know more than just your password. There are many ways to deploy 2FA, and some ways are considered weaker than others (e.g. SMS vs. Yubikey).
Services providers usually give recovery options for users in case their second factor is lost, effectively replacing one second factor for another. But doesn't this defeat any strength in the original second factor?