Developers could also do these processes. And they probably do, often. But they usually have their heads so far up their asses that they don't see how inscrutable this onboarding process is even for very technical users.
It's like when you use one of those Linux phones and your reaction all along is "ew". Do developers not notice how bad this is? No, they don't. Some of them haven't used a good UI ever. They can't fathom it could be better. They really think they are doing a good job.
Why did Discord win? Oh, it must be dark patterns, regulatory capture, moat, etc. It can't possibly be because the UI makes sense!