Define "need"

In my job (infrastructure management) I am constantly fighting against people wanting to throw data away. "We know the condition of the bridge" they say - "so we don't need the past 20 years of maintenance records. It's too expensive to keep".

What they lose is the ability to understand how things change over the long term - how bridge supports and bearings degrade, so they can take proactive steps in the future and replace things in a planned way, rather than waiting for them to break.*

*Actually, what we do is a bit more complicated than this, but hopefully you get the point.