Counter-counter point: Southwest boards faster, by far, than airlines using the standard pre-assigned method. That means less time sitting on the plane, or waiting to board the place. Also means less abuse of selling seat upgrades.
Ever since I listened to that I cannot stop thinking about it when boarding is slow and get upset about the airline making things actively inefficient. A friend made the good point though that a likely reason for the process being chosen despite actively wasting time is that it feels intuitively efficient to most passengers and keeps them happy.
My experience is that American passengers are just terrible. Planes here in Japan board so quickly in comparison, with a standard back-to-front boarding.
At the train station there are markings indicating were the doors of the train are gonna be and people line up at the markings. It makes it really easy to pick a good spot to wait for the train and makes boarding so much less stressful. At least for me. In SF train stops I'd always be strategizing where to position myself and keep repositioning as more waiting passengers are bunching up in certain areas. I'm crazy that way. So Japan was very relaxing for me.
If Southwest covers your route, their fares are almost always going to be competitive with the lowest price. Where Southwest is not good is when you have longer flights (cross country) which will almost always entail stops and or changing planes. But it is great for short stuff like flying between OAK/LAX/SFO/PHX/LAS.