Example: You input a client, you work in their schedule tab, you finish what you are doing and want to pull another client. You often can't do it from the schedule tab, or the pet tab. You have to go back to the overview tab and then input the next client, and then move to their schedule tab, or whatever you want to work on for that client.
It would be more efficient, and save time if you were able to toggle between clients from any tab in the client's profile.