Is it scaled to the founders' local cost of living? Does it assume a 20-something founder with few family commitments?
Or is some of it also intended to cover operational expenditures (at least at MVP-scale)?
What if the founder has a potentially 100x idea, but still wants to go the bootstrap route because... well, let's just say they find Craig Newmark more worthy of emulation[0] than Mark Zuckerberg or the PayPal mafia, and leave it at that.
[0] Although it's worth noting that only the most recent of the competing VC-funded classified ad startups are still around, but craigslist.org is a unicorn.