And TurboTax spends a lot of money on lobbying [1] and advertising [2] to ensure that, first, it doesn't get any easier to file directly with the government, and second, that consumers think "TurboTax" when they think about tax software. The last sentence of your comment is exactly what Intuit wants to engineer.
[2] http://adage.com/article/special-report-super-bowl/turbotax-...
The ads themselves aren't important so much as the fact that they air during the Super Bowl, one of the most effective and expensive ways to make sure millions of people see your message.