Software takes time to develop, and time is money. Tax software is especially bad because 1. the rules are insanely complicated and 2. the insane rules change every year requiring updates.
The real question is why don't we have open-source tax software? I'd argue that since 1. IRS is publicly funded and 2. they have to write code anyway to enforce the tax rules as they change, then they should just publish that code.
At a first step, the tax rules could be published in a machine-readable format.
I get what you're saying here (and generally agree), but I really think it's worth taking a step back when "the law is too complicated for humans to follow it; machine-readable versions should be available" starts making sense.
Imagine if the speed limit was a function of current local wind speed (as measured by one of three airports, depending on the time of day), tire pressure, the azimuth of the sun, etc, and that large companies had digital speed limit signs outlawed. Saying, "Oh, we'll just mandate that all cars carry the necessary equipment to calculate the current speed limit" is probably the wrong approach. The solution is to do away with the convoluted calculation because it doesn't add value in the first place.
The real question is why don't we have open-source tax software? I'd argue that since 1. IRS is publicly funded and 2. they have to write code anyway to enforce the tax rules as they change, then they should just publish that code.
At a first step, the tax rules could be published in a machine-readable format.