It certainly has. It was common practice for BA pilots flying to places like LIN, MXP, VCE and TRN to let people visit on clear days over the Alps for breathtaking views from the flight deck. On more than one occasion the captain would say something like "it's a good view day over the Alps, so we are leaving the door open, do feel free to drop in". Or "we're happy for any children to come up to flight deck, and that includes grown-up children". I'm glad I had the opportunity to do it.

SABENA (Such A Bad Experience Never Again) flight crew rarely shut their cockpit door at all.

As for the original post, I'm a row 1 regular and yes it will typically be airline staff involved, even if they are in mufti. I had a similar experience on Friday going to Scotland with a family of mum and dad, both BA employees, and I guess their 10 year old daughter. Mum on the flight deck, dad in the rear jump seat, daughter under the crew's observation in row 2.