I didn't think they were in the signal path at all... instead simply being a controller for the volume fader which is already in the signal path.
You are technically correct, Herb. The automation controls the fader. Of course, neither the automation envelope nor the "fader" are real things at all, just a stage in the computation chain.
Ambient, the number of things you can automate is staggering. Almost every knob and slider on every plugin and soft synth can be automated. So let your imagination run wild.