You are right. The UX for the Swedish tax filing is sub-optimal, the language is not simple and calculations are unnecessarily complex.
The main reasons are that the tax form comes prefilled, most people don't have to do any adjustments and can just sign it and hand it in. If I understand the US correctly TurboTax does a lot of lobbying against this for obvious reasons.
On top of that filing taxes can be done completely online and when you do have questions the Swedish tax agency is actually one of the most helpful and professional service that I have encountered.
The main reasons are that the tax form comes prefilled, most people don't have to do any adjustments and can just sign it and hand it in. If I understand the US correctly TurboTax does a lot of lobbying against this for obvious reasons.
On top of that filing taxes can be done completely online and when you do have questions the Swedish tax agency is actually one of the most helpful and professional service that I have encountered.