I purge my kegs before filling. But, that is really a byproduct of the sanitation process. Fermented beer at atmospheric pressure has enough CO2 in it to fill the head space.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk