Being "developer-friendly" can be a big draw. Take Stripe for example. It's an HTTP API with bindings in a number of languages. Previously I worked with a payment processor that required we run some sort of Java application even though we weren't a Java shop. Someone had to setup a way to wrap the Java application to interface with the payment processor (not even getting into the issue that now we have to deal with running a JVM-based application). Some companies are actively developer hostile in their interfaces.