Using Services, why is the resource name appended to the endpoint?
See mradcliffe's comment for a good explanation of the difference between an endpoint and a resource, understanding that will make it clear why the Services module does things the way it does.

Why is the endpoint for the user entity type specifically named user? 

Conceptually speaking it's a safe bet that the module developer followed common REST patterns, and adopted the name of the entity as defined by the system the code is sitting in (i.e. the user entity type defined by Drupal core).

From a technical point of view, the resource is named user because the services module explicitly names it as such in _user_resource_definition():

$definition = array(
    'user' =&gt; array(
      'operations' =&gt; array(
        ...


Not a fan of this particular convention? Not a problem, Services has you covered.

Go to the "Edit Resources" tab for your endpoint, and look in the right hand column of the table; you'll see a text field that takes an "Alias". Set that to "users" for the User resource. 

Set your endpoint to something sensible like 'api/v1.0', and you can now access the user resource through its alias at http://example.com/api/v1.0/users. It sounds like you might also want to add a "pages" alias for the "Node" resource, but I'm speculating a bit.