They are fully automatic as i've ran one myself and know this field lol

You need type address manually,Isn't it?

theres automatic upgraders that dont require customers to input their logins

They are not fully automatic.
Your login is only for upgrading, we do not store it and do not have interesting for this.
If you really care about this,you can change your password before upgrade and change your password again after upgrade.

Why does it ask for our Spotify password

We automatically upgrade your account with only one click,It is save your time and avoid any other Incorrect situation.

You can always change your password after upgrade.

I don't know, 5$ is pretty expensive. I remember that such services used to cost 1$... I'll think about it

I remember that such services used to cost 1$ not  exist anymore.