Oracle is not just the database. The have a whole suite of applications to help you run your business from Accounting to Shipping to Inventory to Manufacturing to Human Resources and more. The assimilation of PeopleSoft (resistance is futile) will add to their suite. With their support for these products companies are relieved of the expense of development.
Smaller companies wouldn't have the resources build an Accounting program or to comply with a lot of the government mandated requirements. Tax time would be total Hell. Audits would become a major show stopper. For larger companies they would be overwhelmed with just the day-to-day things that are done and wouldn't have time to do anything else.
Remember, a company must do business to make money and if all of their time is just working on their books they aren't making money. The database is just the repository of the data. It's what you do with it that makes the difference.