We're talking global mega corps here. They are allergic to any real change. If they have an existing AWS contract and can easily spin up these bedrock instances they are going to do that 100% of the time. Vendor procurement is a nightmare in those companies (trust me), and for something as potentially sensitive and hot it will always be easier to stay in the AWS ecosystem. It's easy to underestimate how hard it can be to change something at these enormous companies.