The point is that it doesn't help to know that it was a pilot error, because a pilot is human, and humans in the same situation might make the same mistake - and the main goal is to prevent accidents, not to have accidents happening all the time and saying "it was again human error".
It boils down to:
1 - Was the "error" intentional? If so, how to prevent someone from doing it again?
2 - Was it a real error, with no intention of any kind? If so, how to prevent that someone makes it again?
> doesn't help to know that it was a pilot error, ... and the main goal is to prevent accidents,
You can't prevent accidents if you don't understand their cause. Saying well we don't know what caused it but we'll just tighten all the screws a bit more and send the pilots for more general training. It just doesn't work that way.
Everything is analyzed and tracked to discover the exact root cause. It can often take many years and then new laws or guidelines are usually issued based on findings.
