> I'm pretty sure that simple switch is something directly in the circuit for the fog light, and there is a dedicated wire between the fog light, the switch, and the fuse box. And if its an old Jag, those wires flake out and have to be redone at great expense.

I don't really want to get into a big debate about this as I haven't worked on Jags, but I don't believe that replacing parts of the loom is would be that expensive. Remaking an entire loom, I will admit that would expensive as that would be a custom job with a lot of labour.

> Compare this to the databus that is used in today's cars, it really isn't even a fair comparison on cost (you don't have to have 100 wires running through different places in your car, just one bus to 100 things and signal is separated from power).

Ok fine. But the discussion was button vs touch screens and there is nothing preventing buttons being used with the newer databus design. I am pretty sure older BMWs, Mercs etc worked this way.

Depending on age, it’s more likely that the physical switch drives an electric relay and the relay switches the actual fog lamp current which could be 3-5amps per lamp, letting the manufacturer use a small gauge trigger wire to run to/from the dash and thicker wire only for the shorter high-current path.