How do you know it was correct without being a tax expert? And consulting a tax expert would give you legal recourse if it was wrong.
But, also, the threshold of things we manage ourselves versus when we look to others is constantly moving as technology advances and things change. We're always making risk tradeoff decisions measuring the probability we get sued or some harm comes to us versus trusting that we can handle some tasks ourselves. For example, most people do not have attorneys review their lease agreements or job offers, unless they have a specific circumstance that warrants they do so.
The line will move, as technology gives people the tools to become better at handling the more mundane things themselves.
In a more general sense sometimes, but not always, it is easier to verify something than to come up with it at the first place.