Airbags are not designed with the bodies of children or infants in rear-facing carseats in mind. They're actually really dangerous for them - potentially lethal.
But if you want to get real sad, IIRC many airbag systems are not designed with an occupant outside the parameters of a typical adult male in mind. Some modern systems are getting better about this, but if you're too short, too tall, a woman, or other-wise-outside-of-the-norm, good luck.
Equally when travelling as best I can tell all European cars have a method to do this and you can install in the front seat.
So this probably varies by country, but I am not sure which countries have what or where the USA is.
Without specifically checking I imagine that the Australian Design Rules basically wouldn't allow them to add the option even if they wanted to - if I had to guess because you're not allowed to have such a disable button (which you could argue could also be dangerous in some cases if pressed or used when it shouldn't be).
Also if you take it as exactly 5'9" then airbags aren't suitable for men either. What you need to do is examine the range it's designed for. It's not the average height that matters, it's what percent of men/women fall inside that range. There might be a significant difference in that percent, or there might not be.
According to FMVSS 208, they're tested using an unbelted 50th percentile size male dummy. That's the reason they deploy with more force and are triggered at lower impact speed had they been designed with belted occupants of varying sizes in mind.
If you unplug the cable at the bottom of a BMW seat (so it doesn't know the seat occupancy and belts) it will disable the airbag and show an airbag light.