Granpa Doug
you are correct about the aftertouch. I am one of those old oganists. I have used a pedal for forty years, and have been guilty in the past of riding the pedal. In fact my wife would tell me that I would sometimes tap my pedal in time, which was less than appealing.
I have cured myself of that and use atertouch on more staccato passages. I still use an expression pedal for ogan sounds etc..

The other main reason is overall volume. If I switch to a voice while performing and it is way too loud, I can hit the pedal faster than the volume control and still have both hands to play with. A panic pedal,if you will.
I will concede that it is mainly there as a footrest and panic button,but is useful for orchestral and other legato passages.