Why should anyone hire a lawyer to draft a will? Because drafting it yourself is like driving on the freeway on your first day behind the wheel.
That man contemplating death and writing his own will drives outside of the lines weaving from centerline to shoulder, throwing gravel and screetching tires after his funeral, when reasonable minds differ on what he intended. And, as he is out of the blue and into the black, he cant come back, the only mind that matters is that of the judge. Along for the ride in this inexperienced drivers vehicle is the whole family.
Do you drive a car on the freeway before getting accustomed to car in the neighborhood? How many will writers have litigation experience and know how things really work in court? I mean real court, not the courtrooms on television.
There are perfectly straightforward software packages out on the internet that seem logical and can convey the intent of the will writer well. In that case the will writer is someone in a distant state trying to make a buck out of volume sales without a care really about the end user. Sometimes these things work out.
Sometimes they dont. What if the actual end user of the software wants something other than is in one of these cans? What if there is any complications at all, like a step child, or you have specific ideas about a trust for children or grandchildren that may or may not work in your jurisdiction? What if the national canned will draft is just wrong about the laws in your jurisdiction? The laws of devise and descent are notoriously local.
Hire someone to at least look at what you have written for your last act on earth. The local lawyer will at least know where the speed traps are.