I can think of a few good reasons. Strategic (you don’t want to hand over to a foreign power your critical infrastructures). Diversification (if all your banks run on aws, the day aws goes down you don’t have a banking system anymore). Not being at the mercy of a capricious tech billionaire (what happened to Parler could very well happen to a state if the said billionaire doesn’t like your policy).
I’m unaware of any Core Banking Systems (CBS) that runs on a cloud provider with the exception being Finastra (Azure). Other parts of retail banking stacks? Sure. Not their cores.
The major cloud providers all aim for 99.999% uptime. Keep in mind that 99.99% uptime means ~4 minutes of downtime a month. I think there are other reasons that banks may not want or have the ability to run their core services on the cloud.
The vast majority of retail banking institutions do not run their core. They outsource it to the major core vendors to ‘protect themselves from themselves’.
It’s atypical motivation but one of the few verticals I know of where the cloud is largely out of the equation.
Let's be honest, it's Azure. The only reason you choose it is because either you compete with Amazon in some way, or you hate your infrastructure engineers, or don't know better.
Or because you already use Microsoft mail, so you already have Azure AD there, and they sent you some credits in an email, and then...
I think Azure is cheaper for certain workloads as well, and at one point had DCs in places where AWS didn't. But it's mostly the "we already buy X Microsoft product, and they cost about the same, so..."
From what I’ve seen up until now it’s often the last option. I’ve seen comparisons between the major cloud providers, but those have often been on the level of “I can boot a VM with x cpu on provider y and z”. With these kind of comparisons a major deciding factor then is discounts. And that’s an area Microsoft excels at.
