In this lesson, I discuss a best practice for Profile assignment of users – assigning them to a Custom Profile always, and why that is. As with any software system, or life in general, there’s always an exception, and I share the one exception to this Best Practice as well.
We round things out with an antiquated blog post that gives more history and background as to why you should not assign users to Standard Profiles. What remains a mystery and unanswered to this day is why Salesforce allows users to be assigned to Standard Profiles in the first place.
Use custom profiles where possible [Profile Best Practices] - https://success.salesforce.com/ideaView?id=08730000000GsYf