What's in it for them? Where's the business model for Stripe? I find it extremely annoying that companies - any company - just can't be totally upfront about t

What's in it for them? Where's the business model for Stripe? I find it extremely annoying that companies - any company - just can't be totally upfront about this. "We earn money from this by you having to fund these cards using an account you must have with us, where we get interests. Also by the merchants where the card is used, which have to pay from 1,5% to 3,5% in processing fees" etc. Shouldn't be too hard - I guess they already have this in some PowerPoint laying around.