Why do most forums log you out after registering?

Question

Client side optimization

Common practice:
1. You register on the forum
2. You are asked to confirm your mail
3. You are required to enter a username and password to enter the site.
I don't understand the third point: why require a username and password from the user again if he has already entered them during registration? All the same, after all, the account already exists and the login data is accepted. So what's the problem, start a session, and just change the access rights after checking the email! No, on most sites the settings are different: you register, confirm, and for some reason they log you out.
Maybe there is some important meaning related to security in this?

Answer 1

In terms of security, I see no reason to require a password once again.
I think this is not done on purpose, but simply "it's easier."
Plus there is a small guarantee that the user has remembered (written down) his password.
IMHO.