Data storage without the use of a Database?

Question

Hi, I am building an application using the .NET framework and MS Access for a database. This application is being built for a small business which may not have many users or large amounts of data. The customer recently asked me a question which I could not respond to very well. Any help will be appreciated. The question: Why do you need to develop using a database? (MS Access in this case). Can't you just develop it without it requiring people to own Access or any other Database? How does an application like Quicken work? Why don't you have to buy a database to have Quciken or similar applications work? Thanks in advance.