Ask HN: What is still preventing FOSS Tax Software in 2020

HN, as tax deadlines loom closer in the US, what is preventing a FOSS version of Tax Software?

One that doesn't have any dark patterns and caters to 80% of common requirements majority of the population has. The proprietary software can still cater to the remaining 20% of cases which can be arguably complex.

I'm sure there's tax rules that are constantly changing and keeping up with them is difficult, but I'd imagine this is where social coding such as GitHub etc... would flex its strength.

How would one go about structuring a project like this without it being torpedoed by the current incumbents who arguably wouldn't want something like this to become mainstream.