Exactly. Once you view other teams as your customers, it helps you focus on things like quality, satisfaction, and adding value in a very clarifying way.

And honestly other eng teams kind of are your customers. They may not pay you directly, but they also help to build your product and the company that cuts your (and everyone's) paycheck.

Regarding treating the other eng. teams as customers, I fully agree. I know it's not something everyone does (Been there, argued that), but when you treat them that way and when you deal with their problems (Service xyz requests are too slow, feature xyz would really solve our problems ...) you will, in the end, help the customers.

If my coworkers need my services, then that's because they are developing something that a customer needs. I think of it like a dependency-tree. As long as you trust your company to not have multiple teams develop something that will never see the light of day, or something the user doesn't want or need, then this mindset is absolutely a good one (Sadly been there, done that too).

Yup, it isn't perfect but provided that everyone is largely seeking the same goal (company success) it tends to get you to better outcomes.

Btw this can be true of other departments as well – for example, SaaS product marketing is often an entity that exists to serve internal "customers." Product management can be envisioned this way as well.