Can you really be "just" a hardware company and still compete with Apple, which is both a software and hardware company? Samsung has its own ecosystem of products and services to manage and unify.

If I'm Samsung and I'm trying to compete in the market against Apple, I want to provide as much as possible to my customers, without needing to rely completely on a third party.

Also, when the OS or app on a Samsung has problems, customers don't blame Google, they blame the company that sold them the phone. If I worked there as a product manager, I'd make the same choices to help the company maintain as much control as possible.