Well, they do. For example you can configure your node pool to automatically upgrade its members so you don't have to worry about kernel patches. They have a proxy service for their Cloud SQL product so you don't have to fiddle with configuration, its just another k8s service name. Of course Amazon could do these things but they simply haven't. I think their biggest advantage though is they abstract away the master - you just have a node pool and don't have to worry about the masters. With Amazon you will pay $300 a month just to have a HA master, before you launch even one node in your pool.

Also once you start getting into k8s you will find so much more information in the community with specific instructions for GKE; its by far the best environment to learn in for that reason.

Google falls down in so many other areas though that it probably doesn't matter how good GKE is. The biggest annoyance to me is their Postgres offering still has no point in time recovery.

edit to add: One other big advantage I forgot to mention is that launching a GKE cluster takes only a couple of minutes. I have a Terraform configuration that will launch a GKE cluster and run my deployments and my app is up and running after less than 5 minutes. This makes it much more attractive to do things like spin up a new cluster for each pull request.