Stripe is only available in North America, and probably lacks the headcount to handle thousands or more new merchants in a short time. Braintree's more than twice as old, more than twice as big, and operates in US/UK/AU/CA/EU. Recommending Stripe would mean sending many of Google Checkout's merchants somewhere that can't help them. Google Checkout, like many third-party processors, is heavily used by merchants outside the US where a traditional merchant account is much more difficult to acquire and integrate.