An example would be that the founding team isn't skilled enough to get through the product market fit stage, so they hire in order to fill those gaps. Or maybe it's a chicken & egg problem, which often requires lots of time and luck to crack.
With the high salary requirements that engineers and designers have today, especially in Silicon Valley, this means burn-rates get very high very fast, even with only a few employees.
I remember five years ago in most cases you'd take a major salary cut (which was made up for in equity) when joining a startup as a first hire. You took a big risk to be employee number one or two. These days the landscape is so competitive you not only get equity, but a great salary as well.
I wonder if this has something to do with what you're hinting at?
Do you think the climate has changed since then to make it much harder?