Because for years there has been one application and one database,

encapsulating the data validity and integrity rules in the application has worked successfully. There will continue to be opportunities for these designs.

However, the requirements and resulting architectures are expanding. There are now multiple applications being connected to multiple databases in less tightly coupled ways. The validity and integrity rules must be stored close to the data if there is any chance to manage them cost effectively in this new environment.

Certainly, some of the business logic will be encapsulated in web services that may or may not be closely coupled to the database, but there is now no reason not to keep it close to the database. The design will require careful thought but that's true for any application. Also, the DBAs will have to think more about applications and not just storage management.