People are different

 

The mentor may not be interested in helping others; he might care more about his own job security.  People make connections in their own head, which your generous mind wouldn't comprehend.

Don't complain about the mentor.  Ask your mentor first.  If he is not forthcoming, then ask around, including your boss, about specifics, like who should be at a meeting.  Keep mentor in the loop.  Be always cheerful.