Unifying Web "Sites" and Web Services with the ASP.NET MVC

Why do we have to build web "sites" for humans and different web services for machines? I can create an ASP.NET site, a SOAP-based ASMX web service, or a SOAP or REST (with .NET 3.5) WCF service and while they can share business logic, there's still a lot of "endpoint code" (for lack of a better term) that has to be implemented, and if I want a human friendly front end + a web API, I have to build a site that essentially wraps another service, since the site itself really is a service.