First of all, Excel and Outlook are typically not shared and most companies want one centralized database. Act! allows you to track all of your contact interactions (Notes, Activities, Sales Opportunities, Email Campaigns, etc) in one place. Most importantly you can use Act! to view overall trends within your business to help project and increase future sales. You can use Act! to easily segment your contacts using your specific criteria, and market to one or all segments.
Because Act! is accessible to your entire team it allows you to improve communication, avoid duplication, streamline processes and allow you to implement and follow the processes that will grow your business and retain your customers.