I think it depends where in the World you are. I certainly think there is still that mentality in Asia. Billboards in Thailand this year were full of Air Asia crew showing a little bit of clevage.
But in the US you could be called a sexual deviant for having sexual fantasies about crew as they are generally old or older. In Europe, the image these days is very 'professional'. Virgin is probably the only example where sexual undertones are evident in their promotion but it's as much about the guys as the girls.
Some of the examples you give I don't really agree with.
Air New Zealand. There wasn't 'that' much sexual undertone to their "nothing to hide" promotion. It was primarily done to promote their clear pricing policy and involved employees from most areas of the airline from both sex.
IMO there are nothing wrong with make up stipulations. Most girls/women would wear make up anyway and it's more about just keeping everything uniform and many beauty/grooming products that are more extreme (e.g OTT eye lashes) etc are usually not allowed and red lip stick is banned at many carriers.