Those are usually destroyed when their useful life ends, exactly because someone might dig them up later and extract data from them. Large corporate data centers, for example, physically destroy hard disks and never allow them to leave the facility intact.

There will be hard drives left around by individual consumers, I suppose, but the vast majority of all those that exist today are likely to be deliberately destroyed. We're so good at copying and replicating data these days that we no longer rely on hard drives for data permanence over long periods.