It simplest enought to write this. All you need to do is add a property to your master DocType called (say) "viewCount" that can store an integer (a TextBox would do) and then you can add a Macro (to your master template) that uses the Umbraco API to increment this value by 1 every page load. Not difficult.

In fact, I did something like that once for a Project. At the time there was no Razor so I did it as an XSLT helper. The methods were:

       public static void UpdateViewCount(int id, int amount)
        {
            Document doc = new Document(id);
            if (doc == null)
                return;

            Property viewCount = doc.getProperty("viewCount");

            if (viewCount != null)
            {
                int count = 0;

                if (viewCount.Value != null)
                {
                    int.TryParse(viewCount.Value.ToString(), out count);

                }

                count += amount;
                viewCount.Value = count;

                try
                {
                    doc.Save();
                }
                catch
                { }
            }
        }

        public static void UpdateViewCount(int id)
        {
            UpdateViewCount(id, 1);
        }

 Easily adapted to a razor function.

You can then use Razor or Node API to get values back.

Oh, and I imagine the reason this isn't in the core of Umbraco is that Umbraco is a framework not a CMS as such. Having a heavy-weight stats module that performs a database hit for every page load is not something majority of people would want. Most clients want a proper analytics package and these are better provided by 3rd parties than wasting effort of core team adding it. Umbraco is flexible, so allows you to write your own easily however you want.