[sen]

This is becoming more and more common with major sites, and it’s really bloody annoying. Some are putting “Sign In” behind some tiny dropdown in the nav, not just grayed out or small but invisible unless you hunt for it.

They know exactly why they’re doing though, and I think OP is preaching to the converted. Those doing this don’t need a tutorial explaining how not to do it, they need to lose money (users) until they stop doing these dark patterns.

[mkl]

I don't understand. Why is it to their advantage to have their users struggle to log in?

[bartread]

They probably have metrics suggesting that having both sign up and sign in buttons on the page leads to lower sign up rates than having only a sign up button, or something along those lines.

Rather than find a more in depth/better designed solution, it's easier just to remove the "sign in" button and any "confusion" that might cause for users who would otherwise complete the sign up workflow. If their A/B testing indicates that removing the button improves sign up rates, that's exactly what they'll do.

It's super-annoying and short-sighted - not to mention lazy - but this kind of micro/over-optimisation of behaviour on the web has been de rigeur for at least a decade now.

A better approach would be to try to understand why "confusion" around sign up/sign in is happening - i.e., what's the real reason having both buttons/links on a page decreases sign up rate? Root cause the issue and you can fix the real problem in a way that probably doesn't annoy your customers. That's effort though and most customers probably don't care enough to complain about the annoyance of hunting around for a sign in button or link.