And here's one good reason why:
You write your fiction based on facts. You create monster spreadsheets, track everything, check source after source.
Then you colour in the blank spaces, add a little depth or perspective here and there. You are scrupulous about keeping track of known facts and fictional embellishments.
And then you find another - impeccable - source which contradicts any number of previous "facts", which means either you have to:
1. Change everything
2. Act like you meant that sub-plot to be fictional all along
or most likely
3. Shout a bit. Or a lot.
And when I say "you" I mean "me".