为什么我要使用WSDL来描述Web服务？

I'm having trouble understanding why a WSDL would be so beneficial, when the truth is that the service definition is not that human-readable, and most developers will use automated tools to consume it to generate objects in the application. Why isn't it easier for a service provider to define a simple XML schema, and just tell me in the documentation what I can get and how I can get it? I understand the whole "universal definition" aspect, but it all just seems so overcomplicated to me. Most APIs for social sites use a basic RESTful architecture, and all they do is give you a schema representation of the data you will get back. Seriously, I must be missing something here.I'm having trouble understanding why a WSDL wou