Mostly, they don't. Boarding priority is governed by a few factors, most prominently giving the frequent fliers and first-class ticket holders the feeling like

Mostly, they don't. Boarding priority is governed by a few factors, most prominently giving the frequent fliers and first-class ticket holders the feeling like they're getting their money's worth. Coach is boarded back to front because a) coach is (semi-intentionally) treated like luggage which moves itself and b) boarding back-to-front is faster that front-to-back, in that it has less "person stowing their bag blocks the aisle" moments. Saving 10 minutes on boarding per plane per trip is worth, literally, hundreds of millions of dollars.