You'd be surprised how little volume of api calls payments companies get compared to advertising companies or consumer internet companies. Stripe aren't especially well placed to own this asset on a technical level. That doesn't make this a bad acquisition per se, but there is no magic stripe can inject here as far as infra/technology is concerned.

Agree, even in the payments space usage-billing metrics providers like Chargebee / Lago etc get order(s) of magnitude more data than payment.

Granted payments and associated ledges require a level of consistency that other systems do not require, but that is orthogonal to high volume.

You'd be surprised how antiquainted many of them are. I don't mean Stripe or Braintree but the long tail of terrible terrible credit card processors. If I hear "Chase Payment Gateway" I shudder.