I think the main reason is that most people have very straightforward tax situations, regardless of the amount of money involved. A high earner at a W2 job does

I think the main reason is that most people have very straightforward tax situations, regardless of the amount of money involved. A high earner at a W2 job doesn't necessarily have anything more to report than someone working at a fast food restaurant. The tax brackets are higher but it's really all the same. Different story if you're self-employed, own a business, or are involved in various types of investments.