If try to create an account in any StackExchange site, you will be presented with a signup page, which has Google, Facebook, and StackExchange as signup options.
When you choose and click Google/Facebook, if you are already logged into that website you will eventually arrive at the create account page. Your browser will be redirected few times, but the process is seamless.
But, if I choose the StackExchange option, I am required to fill an account creation form, even if I am already logged into StackExchange.
So my question is, why is StackExchange does not do the same as Google and Facebook? In other words, why I have to give username/passwords when I am already logged into StackExchage? As far as I know all services implement the same protocol.
login instead of
signup takes you to a different page, which has less fields for SE option. But again, Facebook and Google options are seamless.
I expect that when I click SE option for login/signup, it should redirect me to SE site, and if I'm already logged into SE, I should be again redirected to the site I was at the first place. Facebook and Google auth options do this.