Once you hit a certain processing threshold, stripe underwrites you. The benefit is some people get better deals or get to skirt by rules just by being immaterial.

Separately: Once you hit a certain threshold, you get an account rep and can ask for IC+ billing. This is sometimes better than the blended/sticker rate.

And furthermore, once you're really big enough, you can negotiate down Stripe's markup on the interchange. (As with any big enterprise contract).