Pilots are trained to fully understand the importance of getting on oxygen as THE number one priority.
I may add from experience that LH (group) SOP-s take this very seriously.
In pre-hysteria times I have often flown on a cockpit jump-seats with many airlines. I have only ever experienced on LH to be asked prior to push-back to don the mask and test it. It was a part of the SOP, as it happened on all occasions. This may or may not have relevance, but I doubt that lack of awareness or training played any part.