The US has also attempted to do this. However, every attempt has been killed by corporate interests (like Intuit) and politicians (mostly Republicans) and special-interest-groups (conservative anti-tax organizations)
The latter claim that the government shouldn't automatically create a form with all taxes done because the government will not try to minimize citizen tax payments (and most people will check the 'OK' button without reviewing their taxes to see if they can get additional deductions). In reality, I think that most anti-tax organizations realize that they'll lose a significant portion of their support if filing taxes becomes easy. In the case of companies like Intuit, the motives are obviously transparent.