I've had DIY rechargeable lights for 20 years now, so I forget what it's like to rely on expensive disposable batteries.
I'm getting the strong impression that on the Bristol to Bath railway path, some of the ninjas and some of the ones who use their front lights on strobe are trying to save their batteries - at least I hope they have proper lights for the roads before they hit the path. Hopefully one evening I'll find myself in town at a suitable time to witness their antics.
I see quite a few ninjas on pavements out in the suburbs ...
I ride through an unlit wooded park every evening and following storms there are sometimes large branches or whole trees on the ground - not to mention unlit dog-walkers and random dogs, and several times last winter this guy would come through at speed with only a flashing amber light on the front.
If I'd spotted anything in particular, I would tell him so as he passed, but I have to assume he simply had amazing night vision.