NuGet Package doesn't copy files to packagerefence projects

I have followed all the new "contentFiles" institutions, and Nuget package was created and contentFiles/any/any folders there :
[![enter image description here][1]][1]Yet when I install the package on packagerefernece project the content files are not copied.I heard they are not supported only on PCL and universal Apps .I am missing something here ?Apps[1]: https://i.stack.imgur.com/pJuYk.png