In practice it's much easier to move the patient to the ventilator than vice versa, and that's exactly what happens, at least in my country
And then there are the problems of the ridiculously huge countries, like China, the US, or Brazil, that most of the rest of the world simply fail to fathom the enormity of distance-based logistical problems. Two of the largest cities in just the contiguous United States are 4 and a half hours apart at the speed of sound, and there's a bigass mountain range in the middle that you can't fly around. And it looks like a medical helicopter would take about 3 times as long, so moving sick people is a multiple of moving equipment. Even New York City to Chicago would handily kill a patient drowning in their own fluids before they arrived, and most first world countries are wider across than that.