Why do most start-ups die before they're ever launched?
Running out of cash.
Wantrepreneurs at the helm instead of entrepreneurs.
Pressure from "friends", family, etc to chase after the cubicle with fluorescent lighting rather than the apparently riskier start-up.
Fear.
Realizing the idea isn't as good as was originally thought and moving on to greener pastures.
Lack of technical expertise to get the product ready.
Regulatory restrictions that prevent the idea from moving forward.
Crappy credit that prevents the founders from being able to accept card payments, or worse yet, being in a jurisdiction where payment solutions are stuck in the stone age.
Most grim: death of a founder.
However ... a lot of these start ups appear to have just changed their name, been acquired, or otherwise pivoted into something new, which makes it look like hundreds of millions have been poured into companies that have just disappeared. They may not have updated their Crunchbase profile either, so I'm not sure how much stock I'd put in the stats, but I do think it's true that a lot of start-ups fizzle out before they even begin.
At that point you either pivot, or often you start from scratch, on something completely different, something that the founders didn't sign up for. For many it's highly demotivational and perceived as a failure, at which point things just break apart.
I know that everybody tells you that you should be sticking to your original vision, but often a vision that's not backed by thorough investigation doesn't go very far. Often you discover the vision has already been realized by someone else very adequately and you just hadn't done enough preparation. I think at the end of the day, as you embark on your startup journey, you have to all agree that it's ok if your original idea of providing accessible education to 3rd world children might suddenly one day turn into a dating site for foot fetishists. Perhaps that's a much bigger idea (the whole Derek Sivers's multipliers) and you can execute on it much better. Yeah, it's a real bummer that you moved away from that initial plan, but now you might be orders of magnitude more effective.