Nothing is more practical than a good theory. A banal statement, considering that a theory should always enable its users to easily derive the statements they need for practice.
But a theory for catalogs or cataloging? Is that really necessary? A question anyone is likely to ask who has never been confronted with the matter nor considered it with any seriousness.
Using Internet search engines, and knowing their operation is fully automated, people tend to view with skepticism all practical and theoretical effort invested in catalogs. Any good search engine, however, has to be be based on a good theory - though that one may differ quite a bit from a catalog theory.