FWIW, there are plenty of examples on here of female frequent flyers who, when travelling with their male, non-elite significant other, will give him the upgrade. It doesn't have anything to do with chivalry or gender hierarchy. It has to do with the person who's been there and seen that giving something nice to a person who doesn't experience it regularly, and an acknowledgement that air travel is massively disruptive and stressful for people who aren't doing it on a regular basis.
We more frequently see a husband giving an upgrade to his wife quite simply because the vast majority of elite flyers are male.
I totally agree and am often the recipient of this gesture from my wife.