This also includes accounts that you can use to contact friends quickly. For example, the logins to your most frequently used social media accounts.
Put yourself in one of these situations for a moment and play it through in your mind: You lose your device on a trip or it is stolen. Or: The police or border guards take all your devices. What do you do now? Are you able to organize help? What are the first steps?
Knowing logins by heart does not mean that you use simple passwords that are the same everywhere. A short sentence is easy to remember as a password and is still stronger than a simple word.