From riding behind others, I can see that pedal reflectors are effective. However, manufacturers often omit them, especially on the higher-end pedals, and customers do not seem to care either. Myself, I do not buy pedals without them.
Hybrid SPD/platform is not a style of pedal that is to everyone's taste, but I give Shimano credit for having reflectors integrated into the design of the PD-T8000 pedals.
A number of the single-sided Shimano pedal models - even higher-end SPD-SL - have reflector options that can in some cases be not widely available, at least in the U.S. market. I would guess that demand is limited.