And a good thing to!
Pilots are NOT tour guides. They are charged with flying a very large jet with alot of people onboard.
There sole role is the safe flight of the aircraft, not to show Tony and his lovely wife Joyce from next door over the cockpit of a 747 at Fl370.
When I was a kid I was invited up to the cockpit of a Lufthanser 747-400 while in cruise. It was great fun but today there are too many crazed people to allow non-crew into the cockpit.