Found it.
If I access directly to the aspx file so I can check this prop:
Page.RouteData.RouteHandler
is null
where
if I use route url it is not null :
{System.Web.Routing.PageRouteHandler}
Edit
(better solution)
Add those 2 lines to global asax
routes.MapPageRoute("Route", "{*.}", "~/pages/default.aspx", false );
routes.RouteExistingFiles = true;