I would guess this is because the Air Attack was first to market - if you wanted an aero road helmet, it was the only game in town. I got one back in Feb or Mar when they came out, but now have a Course and Evade and the Air Attack will be going to agood home once CX season is over. But others may not be so quick to switch. After all, it seems every day something new comes out that is or purports to be faster. Unless you have limitless funds, you have to pick and choose among upgrades.
Amateur recreational hobbyist cyclist
https://www.strava.com/athletes/337152
https://vimeo.com/user11846099
Amateur recreational hobbyist cyclist
https://www.strava.com/athletes/337152
https://vimeo.com/user11846099