The software hopefully makes sure all bases are covered. There may be powers of attorney, living wills, trust funds, etc involved. If the deceased wishes certain items, possessions, funds, etc. to go to someone other than "by law" (estate divided/distributed to closest relative and then down to the next)...the will would allow that, hopefully without complications.
It's possible a "simple written" will, properly & legally witnessed, notarized, etc., as required by the specific state would be close to (if not?) legal as well?
If one's estate has to go through probate, that can cause problems & hopefully a properly written/completed will would prevent those problems.