Why? You're not expected to find a tape in the attic 40 years from now and insert it into a drive you just bought at Fry's and restore the data from it.
If you do care about the data on any given medium a few years from now, you copy it then to a current medium. And so on.
This works fine as long new media are cheap, easily available and higher density than the old. As has been the last sixty years. If this progress ever halts or reverses (due to some man-made or natural disaster, including a major economical recession), we're screwed.
Doesn't matter what is expected to happen. Some time in the future someone needs to recover data from some old medium, proprietary format hinders that effort significantly and unnecessarily.
Not to mention the closed format causes reduced competition in making better or cheaper devices, which is another downside.
If you do care about the data on any given medium a few years from now, you copy it then to a current medium. And so on.
This works fine as long new media are cheap, easily available and higher density than the old. As has been the last sixty years. If this progress ever halts or reverses (due to some man-made or natural disaster, including a major economical recession), we're screwed.