So what do I want ? For authentication there are some common requirements:
- session/cookie management to store a user ID (or other info)
- hooks/middleware/whatever to allow me to check user credentials on each request
- safe hashing/encryption of passwords
- form processing/validation
- integration with OpenID, oAuth, LDAP etc
If a framework, or libraries, provide these then that saves a lot of time and effort, and allows me to create a tailor-made solution.