I'm sure that this kind of confidence existed in the general population several times before. I bet the people of Pompeii never thought they'd be in the path of the lava too.

Sure, I could probably work backwards from what I can remember to recover a lot of technologies but I'd rather not leave it to chance.

Nostalgia is another benefit of keeping old tech around, especially when the old tech carries the information about how to build the new tech. I mean, transistors... I could probably figure out how to make them out of valves, given a few years and endless resources but a manual on how to print at least 1980s era ICs would be a hell of a lot more useful.