Every CEO, board, and middle manager in the world is AI buzzword-obsessed now. Surely asking to sign a contract with the frontier labs directly would not get held up?
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.
If you're an engineer in the trenches of the company, good luck convincing the people above to sign that contract. You'll waste thousands of hours just trying.