well, they definitely don't appear out of nowhere. I agree that a lot of stuff in History is basically "story", but that doesn't mean we should throw in the towel.
https://en.wikipedia.org/wiki/German_tank_problem
edit: thrown->throw, still sounds wrong
Throw is right. English is a fairly odd language and it gets a whole lot worse when you use idioms...
The thing about hard data and history is that, while it can be hard to generate, there is plenty of it out there. The use of hard data can be very useful to correct and adjust the more 'narrative' elements of history - the German Tank Problem being a classic example of this issue.
Data, however, does require analysis and understanding to correctly interpret - their are many, many poor analyses out their that rely on data that does not support the conclusion. I think the lack of good statistical education found in most university courses, including many Science degrees let alone History, is appalling.