[majormajor]

Historically the progression has been (oversimplified):

some sort of reciprocal/mutual aid economy -> exchange (usually external) -> joining in with currency and capitalism

In my view the clear main factor is external disruption that forces groups into the market/currency based economy. That, plus the difficulties to control bad actors if you had a more informal system at huge scale (millions of people).

Without the external economic disruption you simply just don't get much diversity.

As far as specific events, things like disaster assistance volunteer operations in the West tend to be both religiously and ethnically diverse yet performed independently of expected remuneration. Otherwise it's not like we're observing huge samples if we restrict ourselves to looking just for communities that have both been religiously and ethnically diverse. Is the failure of any such alternate community to last for centuries - when the opportunity has barely even been there for that long - conclusive at all?