The world, even excluding SV, has more good programmers, but existence isn't enough.
> but the more places you're willing to recruit from the better
You're ignoring cost.
If local matters, then moving cost and "number available" matters.
There are many places with "enough" programmers to do {reasonable size project}, but there aren't thousands, even if great programers can be found almost anywhere.
There are fairly few places where there are "enough" programmers to do almost anything. SV is one of them.
> but the more places you're willing to recruit from the better
You're ignoring cost.
If local matters, then moving cost and "number available" matters.
There are many places with "enough" programmers to do {reasonable size project}, but there aren't thousands, even if great programers can be found almost anywhere.
There are fairly few places where there are "enough" programmers to do almost anything. SV is one of them.