Could this be because Stripe has to sell, essentially, to developers, not executives, unlike most B2B products? Developers love slick product pages as much as the next guy, but none of that matters if sales are made over golf sessions with executives.
Although I personally feel it may just be innate appreciation or love of the craft. It's interesting to compare Stripe with other providers such as PayPal, AWS/Amazon, Square. AWS is (and has been) focussed on selling to developers, startups to massive companies. Yet, their product pages aren't as slick as Stripe's. They built out their product with the ethos from the Retail side -- frugality, ship fast & often etc. ¯\_(ツ)_/¯
