Many web properties are no longer accessible due to M&A activity and Small/solo publishers unable or unwilling to maintain their assets. Archives like WayBack Machine mitigates some of the loss of digital content so long as the archives themselves are still maintained.
Will spinning rust be as durable as Microfiche?
Digital makes it cheap and easy to have multiple in many locations. While any one media may fail, you still have a copy - I have on this computer all the data from whatever computer I was using 15 years ago. (most of it I have not looked at in 20 years and I could safely delete, but it is still here, and on other backup systems I have)