Without templates, Document Creators in your business have little choice but to create every new document from nothing, or copy and modify an existing document.
Creating a new document from nothing requires significant effort just to ensure that the correct branding, styles, and messages are used - and that's before the actual content is considered. Copying and modifying existing documents creates significant risks, including inaccuracy which at worst can expose your business to legal and financial repercussions.
You might also have software applications that create documents without templates, and carry the document's formatting & content embedded in their source code. Your business can't respond to regulatory and market changes in a timely manner if changes to your documents are restricted by long development and maintenance timeframes.
Templates are based on a 'simple' concept: the template is a model of the type of document you want to create, and usually incorporates placeholders where data is added - names, addresses, dates, in fact an infinite variety! - to create the document. Merge the template with the data, save the result, and your new document is ready. In practice, templates are rarely 'simple' but the concept still applies.