Aside from receiving your income tax refund faster, there are many reasons one would want to file their return early within tax season. For one, if you do so and find you have a tax liability, you have until the original filing deadline to make a payment, which allows you time to make plans and collect funds for the liability if necessary. Additionally, it never hurts to have all your documents in order in the event you have to have a financial review for whatever reason (eg. signing up for a mortgage or applying for financial aid). Also important to note, filing early reduces your exposure to identity theft, as others have less time to attempt to file a return using any stolen information they may have on you.
For practical reasons, filing early generally reduces your stress levels at tax time and allows for less competition when trying to get your tax preparers attention, who are often overwhelmed as the April 15 deadline approaches.