Is WS-MetadataExchange Really Necessary?

I'll admit it: I don't really get WS-MetadataExchange (or WS-MEX, as it's affectionately known). I understand why someone might want to get the Schema, WSDL, and WS-Policy data for a service. I'm just not clear on why a simple URL isn't good enough. Why do we need to invent new RPC-style request/response pairs?

I guess I can see that this allows me to have one URL for the service that can be interrogated for all three in a standard way. Otherwise, I have to tell you three URLs to give you the metadata instead of one, but couldn't we just as easily agree to some kind of convention like this:

This seems much simpler and easier to implement than a request response pair. Plus, I can still grab each of these important documents in a browser and inspect them when I want without having to have a special tool. Am I missing something?