Having a pre-filled form you could look over and send back is suggested occasionally, but seems never to pass.

This is the norm in New Zealand, simplified greatly by our tax code which is inifnitely less complicated.

The nefarious explanation for why is that Intuit has good lobbyists [1], but I'm not sure how true that is.

I've seen the topic come up on left-leaning US sites like Metafilter and it seems that in the US even nominal lefties who approve of big government are paranoid they'll miss out on their tax dodges if the IRS prepare the form for them as a first step.