Because our Federal government is super good at creating easy to use, functional websites.

TurboTax was able to hook into my investment accounts and automatically pull all of my data. It worked great. All the IRS needs to do is provide an API to let a range of software do the same.

Also, use of "average" here is criminally misleading. The "average" person doesn't spend $200. And the "average" tax return isn't $2000. TurboTax free edition is perfectly sufficient for a plurality of users.