The problem is, would "ordinary folk" want to pay for extra external storage? Would they even know what RAID is (or not think it's just a bug spray)? You have to remember, "ordinary people" are not as tech inclined as we are.
How would they react to now having to plan, far in advance, on renting a movie? No more instant gratification like you would get by going to a rental store or buying a movie, spur of the moment.
Currently, when someone's dvd player dies, they can easily buy another one. If a hard drive dies, you've suddenly lost your entire movie collection. How many "ordinary folk" would know about backup, be willing to pay extra to be able to backup, be diligent enough to backup? Digital copies are not as stable as physical media and not as "simple to use and understand." If you think in terms of "ordinary people," the masses will have a problem with this.
This also would kill the "used cd/movie/game" secondary market. You'll be paying more and getting less. Would ordinary people stand for that? ...Maybe, in the long run. Physical media will most likely go away eventually....but not for a long, long time. Not until there are nearly instant downloads at half the cost of what we are paying now. Digital distribution is too slow and too expensive for consumers right now.