Because it's largely a boring coding task that requires painfully complete understanding of stupidly obscure tax codes, running research into tax courts to see

Because it's largely a boring coding task that requires painfully complete understanding of stupidly obscure tax codes, running research into tax courts to see how these codes have been interpreted into law, etc. I'm not sure about the US, but other countries have certification that must be passed before they're even allowed to sell/provide their product to meet the government tax guidelines.