Specifically it is lacking USB 3.0 support. The reason is that Windows 7 starts to be rather old already and the basic installation does not support more modern hardware. Installing Windows 7 on the NUC5CPYH or NUC5PPYH (Braswell NUC) is a bit tricky.
The following instruction tells you how to install Windows 7 on a Braswell or Skylake NUC.