We don't know how effective the launch escape system is in a pad explosion. It might only save the crew 50% of the time, or 10% of the time. If we assume the l

We don't know how effective the launch escape system is in a pad explosion. It might only save the crew 50% of the time, or 10% of the time. If we assume the launch escape system is unreliable, then the numbers strongly point towards loading the crew after the rocket has been fuelled. The crew avoid the riskiest part of the process, and they are on the rocket for a shorter amount of time.