Business continuity: Providing a good SLA isn't in the AWS business model, which allows for widespread, lengthy outages. They have a so-so SLA and if they miss you get AWS credits, big whoop. They make their money on people who are insensitive to high cost, middling performance and reliability. Not sure about the other providers. At a certain point it's cheaper and easier to do it yourself than to support a hybrid cloud approach that can survive those events. Financial services businesses can afford the higher quality.