It's a problem 99.9% of people don't have now, but could have at any time. Seatbelts are also a solution to a problem 99.9% of people don't have, but that doesn't mean I don't want one.
(Is it profitable? Maybe not -- look how few people make backups now. But that's distinct from not wanting to have had it.)
You, sir, have aptly described the difference between vitamins and painkillers. Tylenol (one painkiller) is bigger than the entire vitamin industry. The whole industry.
That aside, in the "vitamin" world, I think success is based on how likely you are to have that problem. Everyone knows someone who's gotten in a car wreck. Everyone knows someone who has had a hard drive crash. How many people have had Flickr accidentally wipe their photos? If you're selling risk mitigation, it's gotta be pretty risky.
+1
The OP says why YC won't fund him (single founder, no biz model), but he's overlooking the doozy. YC has freakin' T-SHIRTS that say "Make something people want". Not is this addressing a problem that 99.9% of people don't have, but it's also something that the big web properties don't want (for a number of reasons).
Solve problems. Solve painful problems. Or, if you're more consumer focused, get smart about dopamine.