Comment by garethmcc

Its not as simple as that. Just because its the case of "we have lots of old stuff" doesn't mean you need to ignore the new stuff. Building solutions with traditional data centers and staff, even if you have a lot of it, is often a lot slower. You can spin up entire fleets of servers (or even use services such as AWS Lambda, API Gateway and DynamoDB so you never use servers) and get a solution out in much less the time. Its not just about responding to load but also to be fast enough to get new stuff out there. Traditional financial services organisations are notoriously slow to adapt to changes in the market. Using cloud resources alongside the legacy infrastructure is one way to try and remain competitive.