The main purpose of implementing a Document / File Management Systems is that of helping an organisation manage the cost and the risk of owning documents and files. 
Every organisation has some sort of document or file. The bigger the organisation the bigger the variety. These can vary in form such as physical paper received through regular post, notifications and information coming through email, documents that have been printed and placed on a desk as well as documents created in soft format already sitting on the users' laptop.
All of the data above is vital to an organisation and it is this same data that carries risk and cost, both of which are factors that increase in volume based on the size of the company as well as the importance of the information itself.
Here is a map of all the costs and risks associated with files and documents:
cost and risk of documents 
Each element within a red circle within the chart constitutes of a cost aspect. Each of which grows with the growth of a business. The items marked with an exclamation mark highlight the risks of owning such information (be it in paper or digital format).
Document management solutions help in reducing such costs and risks and making them more manageable.