> It's hard enough to read data from a drive built 20 years ago!
Because you don't have the hardware lying around right now. It's still quite possible to read all popular formats today and most of the ones you mentioned can even connect to the same SATA bus available on basically all normal mainboards. And those are mediums which are built for ~10 years (you'll find bit rot by then, which is what is actually preventing you from reading the data). Tapes, for example, are meant for long-term storage, are still in use and can be readily read.
To add to this, books have the same problem. Have a look at the declaration of independence: The font and language is already quite different from what we use today, and that's only from ~250 years ago. Plus the paper would probably not hold up to normal handling anymore.
Because you don't have the hardware lying around right now. It's still quite possible to read all popular formats today and most of the ones you mentioned can even connect to the same SATA bus available on basically all normal mainboards. And those are mediums which are built for ~10 years (you'll find bit rot by then, which is what is actually preventing you from reading the data). Tapes, for example, are meant for long-term storage, are still in use and can be readily read.
To add to this, books have the same problem. Have a look at the declaration of independence: The font and language is already quite different from what we use today, and that's only from ~250 years ago. Plus the paper would probably not hold up to normal handling anymore.