Because SketchUp Terms of Service and the Software Requirements (quoted below,) makes clear that running SketchUp under virtual environments is restricted and not supported.
Virtualized Environments
At this time, SketchUp doesn’t support operation in a virtualized environments such as VMWare or Citrix.
Per the SketchUp Pro Terms of Service: You may not use or host the Software in a virtual server environment.
(Ie, it is not designed to run that way. It saves settings to the user hive of the Windows Registry, registers it’s filetypes in the Registry, needs to write a license information file to it’s %ProgramData% path, and needs access to the machine’s NIC adapter to complete license setup.)