It's an option. You can have solution explorer select the current document. FYI, this option existed in VS2012

>Not sure if everyone else has noticed it but there is something nice with Visual Studio 2013. Before, when you clicked on an item in the Solution Explorer, that item was then shown in the main window, such as a Test.vb file or a Test.aspx file, for example. But, after you would close the last one, the pointer in the Solution Explorer would go back to the previous state. This was quite irritating as we were losing the place where we were at in there. Now, this is no longer the case. It stays where it should and that is nicely welcome.