Auth

"Basic login" using what?

E-mails as usernames?
Some user-defined pattern for custom usernames?
Via AD/LDAP? Via OAuth?
Passwords hashing via bcrypt, scrypt, pbkdf2?
What if there should be an IP address based restriction?
What if you need to tie it to some other application specific logic?

These are all questions related ONLY to a possible login() method, I'm not even going into how it would have to couple it to cookies, sessions or some other kind of token exchange.

It's only basic after you make those decision and CI as a framework should provide generic solutions while leaving the choice to you. With authentication, this is just not possible and as long as I'm involved with the project, such library will not be included.

I agree with this.

I designed something that works for me and recently cleaned it up and released it in the add-ins section (Appunto-Auth), but there are so many ways you can take something like this that it would be very difficult to foresee the needs of every individual application without creating something that would become overly complex and bloated.

I want to add more features to mine going forward, including making it work with CI3, but sometimes it can be difficult to decide where to start.  Multiple database compatibility? Integration with FlexiAuth?  User Profile pages?  System for allowing addition of custom user data? Login tracking and reporting? IP banning?  etc etc... 

I haven't even gotten to a user password reset feature yet and there are like a dozen different ways to implement a common thing like this.

I think it's a good idea to keep this out of the CodeIgniter framework so developers have a wider array of options and can choose something that works best for their application.