I guess I consider it more important for the URL to describe the
end resource that it's providing, than for it to describe the
underlying protocol(s).  We don't have tcp: or ip: URLs; we have 
URLs for higher level services.  Some URL schemes don't imply a 
particular protocol.  However, for every URL scheme that uses the 
name of a protocol, the URL names the highest layer protocol 
on the stack, rather than some lower layer.
Keith