i haven't done a lot of primary training but I've done it as a matter of course. It introduces the family member/friend, typically a spouse, to flying in a situation in which he or she feels more secure (an instructor on board).
It directly helps with parts of the training, for example, rudder use. Bad rudder use is in large part due to the front seats being just about on the CG, so we really don't feel uncoordinated flight that much. I give the back seater a rolled up newspaper, explain the phenomenon, and instruct her to whack the pilot in the back of the head if she feels her butt slide during a turn.
I'm not worried about the FAA considering it a tour. Insurance depends on the insurance contract. The ones I've looked at haven't concerned me. But that's me. YMMV.