This is a quote from the book
Delaware Laws and Programs Affecting Business by Richards, Layton, and Finger.
IV. BUSINESS LICENSES
In order to engage in most categories of business or occupation in Delaware, a Delaware business license must be procured. The annual fees for these licenses vary, depending on the business or occupation and the number of branch offices. In addition, there is normally an additional license fee based on taxable gross receipts or rental payments that varies in rate and amount of allowable exclusions depending on the particular business or occupation. (See Chapter Four, "Delaware Taxation---Gross Receipts Taxes.")
They have this url on the back of the book.
www.rlf.com Perhaps you will find more info there.
Many large companies do choose to *incorporate* in DE. Disney is a well-know example. They do not conduct business directly from Delaware. Incorporating in DE is less expensive, and the legal system is supportive.