Professional tax preparation helps a client get all of the tax deductions he/she can legally deduct. With the tax laws changing constantly, this is important in not only maximizing deductions, but minimizing chances of taking deductions that are no longer allowed by the IRS. Tax preparers are more familiar with the latest tax guidelines and rulings, plus they have the experience in doing many more tax forms for clients with similar tax situations.
Many people who choose to do their own taxes make mathematical errors that can cause problems with their refund, delay their refund, or cause them to possibly overpay their taxes. According to the IRS, most tax return mistakes are the result of MATH errors.
In the event that you get audited, a person who had filled out their own return will most likely have to hire a tax professional or CPA to "reconstruct" their return and also go with them to the audit... this expense will most surely cost a lot more than if the tax professional had prepared the original return in the first place! If my Memphis area clients are audited, I go with them free of charge.
Peace of mind is another reason why more people are choosing to let a tax professional prepare their return. A once-a-year specialty service like tax preparation that requires a certain knowledge and discipline can best be performed by a person who is skilled and experienced in that line of work.
Also, you have the benefit of a 3rd party who can provide some advice, guidance or suggestions (when applicable) as to how you might minimize your tax liability in the future (not offered by all Tax Services).