Back in the day – when the Internets were exploding and I was still coding – I worked in enterprise architecture. Enterprise architecture, for the record, is generally not the same as application development. When an organization grows beyond a certain point, it becomes necessary to start designing a common framework upon which applications can be rapidly developed and deployed.
Architects design and implement this framework and application developers then code their applications for deployment on that architecture.
If that sounds a lot like PaaS it should because deep down, it is.