Using templates significantly save the time of generating documents of the same type. For this purpose, there is a special feature named Mail Merge. It allows you to easily generate a bunch of documents based on a template.
Let us say, we need to create an app which generates hundreds of identical medical certificates in PDF format.
Create an each PDF document programmatically in a cycle and insert personal data (First Name, Las Name, SSN, Date of Birth ...) from DB or a collection.
Actually, it's not so easy programmatically create document with a nice desing. And with future design changes, you may feel the difficulties to maintain this application.