It would be very difficult to show the safety side of the cabin crew position in an ad without potentially scaring many passengers. Perhaps that is why you won't see a commercial of showing an evacuation, or a crew doing CPR, or restraining a passenger having an overdose, or breaking up a couple who are fighting, etc. No-one is going to fly with an airline that confronts it's public with the realities in such a way, even though all airlines deal with the same issues regularly.
Probably the closest I have seen was a BA ad from around 1999 where a group of school children were playing musical chairs. Each child depicted had a caption of their future career. One boy missed out and started having a tantrum. A girl stood up and let him have her seat. Her cabin was something like 'future BA cabin crew member'.
Personally, I hated the ad because I saw it as rewarding bad behavior but I did show something beyond ordinary cabin service, ie: putting yourself out for the benefit of others.