There's also login passwords, and depending on how many systems you have to log into, these can be quite numerous. There are some attempts to address this with smartcards and FIDO tokens and so on, but it's not nearly universal yet. At least SSH keys are common for remote login nowadays, but you still need to log into some computer directly first.

I find it rare to have a huge number of machines to log into that aren't hooked up to a centralized login server. Still, nothing prevents you from having passwords for each individual machine that needs it. It's cumbersome to type it in but it works, which is why I recommended all lowercase (faster to type on a mobile device).