I don't know why airbags aren't opto-isolated digital devices activated by simple challenge and response over canbus (read a single byte off address 0, write th

I don't know why airbags aren't opto-isolated digital devices activated by simple challenge and response over canbus (read a single byte off address 0, write the same byte back to address 1 to trigger). I'd have expected pyrotechnics to have been first on the list for conversion to digital.