Many AWS customers use separate AWS accounts for their development and production resources. This separation allows them to cleanly separate different types of resources and can also provide some security benefits.
Cross account access makes easier for you to work productively within a multi-account (or multi-role) AWS environment by making it easy for you to switch roles within the AWS Management Console. You can now sign in to the console using your IAM user name then switch the console to manage another account without having to enter (or remember) another user name and password.