Solution Navigator from the Visual Studio 2010 Productivity Power Tools first merged Solution Explorer and Class View. It added the ability to expand code files to navigate to its classes, expand classes to navigate to their members, and so on. In Visual Studio 2012 and Visual Studio 2012 this functionality became a standard part of Solution Explorer:

Classes and methods in Visual Studio 2013 Solution Explorer
Still some people never use the Solution Explorer to navigate the code symbols and methods. In this case expansion arrows on code files only create distraction in the Solution Explorer window. There is no option to control the availability of file expansion, but there is the UseSolutionNavigatorGraphProvider dword registry value (discovered by Julien Lebosquain) that you can set to 0 to disable class view in Solution Explorer. The registry key for this value is HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0 for Visual Studio 2012 and HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\12.0 for Visual Studio 2013 correspondingly:

Folders and files only in Visual Studio 2013 Solution Explorer
Now you can select the better view for yourself.
Update: See Hide class info in Solution Explorer command for Visual Commander that works with Visual Studio 2012/2013/2015/2017.
Does this work in Visual Studio 2013 RTM?
Yes, it works in VS 2013 RTM. Just select the 12.0 registry key for the modification.
doesn’t work in vs2013 ultimate. Once you start vs2013, it deletes the key !!
Strange. I’ve retested in VS 2013 Ultimate and it works on my machine. I’ve created a reg file with the key to make sure we use the same settings: NoGraphProvider_VS2013.reg.
Yes I was using the same settings.
I found out what was the problem. The extention VsCommand 2013 is the one deleting this key on startup !
I recently had a problem with VsColorOuput because of this particular version of VsCommand.
There is an option in VsCommand 2013 to “disable graph provider”.
There was no key by default in registry, but adding it manually (for VS 2015, which is 14.0) solved the issue.
Thanks to Sergey and Julien
Thank you all!
Works also with the VS 2017