Good post on a very useful SAS feature Rick!

A benefit in using a user-defined format is simpler management of your business definitions. If you have your format definitions centralized, and a change is required due to business reasons; for example the bounds for middle income change, you only need to change your proc format code and not all your individual SAS IF-THEN/ELSE statements.

This approach ensures consistency across reports and analysis and gains business trust as the same definition is used rather than multiple static definitions scattered across code.