I posit its even more than that. It's a meme / propaganda by the survivors with their bias and those who hope to follow in their footsteps.
Also what's also interesting is you posted your comment to a throwaway while the others parroting that talking point were happy to reveal themselves at least pseudonomusly.
I'm pretty sure why. You don't want to burn your shot if you want to have another go at the startup thing and have people be able to read you saying you wouldn't be fully committed.
I fully respect that.
The only reason I point it out is to show how Silicon Valley the larger VC ecosystem is an echo chamber around this ethos.
My guess as to why is how would they recruit the next generation without that?