They often provide that consulting for free, and we know their biases. There's nothing hidden about the fact that they will push us to use AWS services.
On the other hand, they will also help us optimize those services and save money that is directly measurable.
GCP might have a better API and better "naming" of their services, but the breadth of AWS services, the incorporation of IAM across their services, governance and automation all makes it worth while.
Cloud has come a long way from "it's so easy to spin up a VM/container/lambda".