Why do so many people think payments is the key to monetization? Is it really as dumb as "it involves money"?

Payment processing is a total commodity business that is super-resistant to increasing its tiny margins, which is what would need to happen to monetize it to the tune of a 10 digit valuation.

In comparison layering advertising or premium features on top of messaging is a much more feasible way to generate revenue, since that is pure margin. It's not a superficially sexy / hand-wavey though.