At the end of the day, all of AWS is simply "I wish to mutate the state in your cloud such that your cloud will subsequently respond to request X with response f(X)." At the end of the day, that's an API. It's just that you're also warming a "cache" that happens to be Turing-complete :)
People also need to realize that you could make the argument that the massive behemoth that is AWS is just an API company. They give you simple APIs to perform actions (in their case that might be to spin up a compute node, etc).
In the Sendgrid example, they give you an API to send an email.
So it’s about companies who create services and the customer touch Point is only an API