Just like before I can lose entire tv series when the disk fails.
If you're worried about the drive failing, a RAID-1 setup will take care of it, while doubling read speeds and halving seek times.
If you're worried about user error or other accidents, have one offline in an external caddy, and just periodically power it up and rsync all the new data to it.
I've been doing the later religiously for the past 10 years, upgrading my external drive every time I upgrade my internal drives. In all that time, not one hard drive has suddenly failed on me, instead bigger drives drop in price and become too tempting to ignore, so old drives go in the trash. But besides being insurance that my many years of acquiring content won't poof into smoke and leave me at square one, feeling like a crippled baby learning how to walk again, the external drive has been extremely useful in making my hard drive upgrades, and OS upgrades, a much simpler operation.
It's just so damn incredibly cheap and easy to keep a reasonably up-to-date backup of EVERYTHING you have, that I can't believe people would choose not to do so. The prices on "cloud" storage are astronomical by comparison.