I've come across a TON of clients who have never had their makeup (more specifically, their foundation) airbrushed. People recognize that airbrushing is popular and desirable, but most of them don't know why that is. These are a few of the reasons why I, personally, offer airbrushing as a standard service during all of my makeup applications:
1) Flawless finish. I think a lot of people can agree that one thing they worry about or dislike, is when foundation is noticeable in a negative way. Whether it looks caked on or feels caked on, nobody got time fo' dat. After I've airbrushed a clients foundation, I often hear comments such as "It doesn't even feel like I have anything on my face" which is ideal. And it is the closest you'll come to looking like you were born with a perfectly even skin tone, free of blemishes.
2) Serious longevity. Once the tiny foundation particles fly out of the airbrush and land on your face, they cling on for dear life. I don't know why this is, honestly. But I know it's true. I've applied makeup on a client 7 hours before an event, and she informed me that the makeup stayed put into the early hours of the next day.
3) Easy colour matching. This actually makes my life about 20 times easier. When you're applying your typical run of the mill foundation, if your colour selection is even slightly off it stands out like a sore thumb. If your neck and chest are one colour, and your face is a different colour, people have an easy time playing the "one of these things is not like the others" game at your expense. But because airbrushing applies the foundation in such a light mist or veil, it's much easier to blend it out on your neck or chest. So even if the foundation isn't an exact match (you still want it to be close, obviously) it's more likely that it will look correct.
Here's a video I threw together, using my friend Sandra as a model, to show you what it's like to have your makeup airbrushed.