Why do I still need to use an Intuit ID to log in to or register Quicken 2017?

Quicken for Mac 2017
Quicken for Windows 2017

As of April 2016, Quicken, Inc. is a new and separate company from Intuit.  Though Quicken, Inc. is a now a different company, user authentication is still crucial to many of Quicken's connected services. To prevent any disruption to Quicken users, Quicken has continued to use the Intuit ID for user authentication.  

Our plan is to have all supported Quicken products moved to the new Quicken ID service by the fall of 2017.  We're taking the time to make this transition to the new Quicken ID as painless as possible for users, while continuing to deliver a high level of security for connected services.  Until then, we'll continue to rely on the Intuit ID to provide you with secure connected services.