Turbo Tax also provides some kind of service to help you if the IRS comes after you for some errors. One of my friends paid extra for this, him made a simple calculation error in their tax return, the IRS came after him for it, and Turbo Tax didn't do shit because he made the error, not Turbo Tax. So they're giving you the opportunity to pay them extra to cover the cost of their mistakes.
I honestly think more people would be willing to pay higher taxes if the process was low-effort for most people. For example, if you work for a company that witholds taxes from your paycheck, you shouldn't have to do anything; either you get a check in the mail if you over-payed, or a bill if you under-payed, and you answer a yes/no question to adjust your W-4 for the next year.