No one here seems to have mentioned what I think the problem is.
Old hard drives seem to last longer because Windows XP or Vista with its constant hard disk churning didn't exist when they were in their prime.
They had nice efficient OSes like Amiga Workbench and other OSes which did not grind the disk so much.
I have people who have had the exact same hard drive in a Windows and another system, both purchased at the same time and used regularly, guess which one died first?