Also, when others inherit the media they may not have proper equipment or skill to do it themselves as goal of the preservation is to get it 100 years ahead, not keep it always in a usable state per se. For example, I'd like my children to keep my backups until my grandchildren could access them 60 years later.
For book keeping, I think my point is that storage media are becoming so big that you always consolidate into a single device every time you carry the data over (you may still want to duplicate for reliability). Like you can buy a 18TB hard drive today. A consumer isn't going to require more than one or perhaps two of those for anything to be preserved long term. And in 5y-10y, you will likely have 25-30TB hard drives.
The equipment problem is precisely what this addresses. You are always using the latest hardware, and the previous hardware you are using is still supported if you stick to a 5-10y cycle. For instance you would have moved away from IDE drives while you could still find motherboards with both IDE and SATA ports. But if your data is stored on an IDE drive, good luck connecting it on a computer in 2030 (if we haven't moved full Apple's "you can't customize your hardware and we deprecate everything very frequently").
Skills (and I would say mostly dedication) is still a problem. But we are talking about copy-pasting files between two media, it's not rocket science even if you don't script it.
Every 10 to 15 years, you send in your archived (and new/interim) personal data and get it back on the current top-tech storage medium. That way it's not stored in the cloud and you can keep moving the stored data forward without having to deal with it all yourself.