So the first electrostatic generator was made in the 1660's, but steel was first commercially produced in the 1800's. Avoiding the Baghdad battery issue right now, let's discuss that the Egyptians, Greeks, Romans and Arabs knew of electricity and its conductivity through metals before 0AD. The Greeks were using shocks from electric fish to try and cure headaches and gout.
Magnetism was a well known effect, in the beginning of the iron age. Why? Because non-quenched iron becomes magnetic along its length.
Steel was first commercially produced around 300 BC in India. It wasn't
mass-produced until the 1800s because that's when mass production was invented.
And knowing about electric fish and compass needles does not amount to a
technology. It's a long way--a couple thousand years, even--from building any kind of electrical machinery, which, let's face it, is what people are thinking about when they talk about "electricity in DF".
Besides the fact that there's steel, perpetual motion, adamantium, etc that makes no sense in a 'middle age' setting.
Steel existed in the Middle Ages, perpetual motion is technically a bug, and adamantine (note spelling, please) is a fantasy setting element. The real Middle Ages didn't have kobolds, either.
We're discussing a material property here. Even if he doesn't want to provide a use for electricity in the game it should still be in the game for a simple lightning system.
The simple way to simulate electricity is to add conductivity and dielectric constant as material properties and use Ohm's law everywhere and
this will not simulate lightning. Assuming charge somehow builds up in the sky, it will either stay there forever or uniformly bleed off through the air, depending on whether the air is conductive at all. I suppose you could build a copper spire to the highest z-level and short out the entire atmosphere, which would be Fun, but other than that, it won't do anything.
The only way to get lightning, short of a really beastly physics simulation, is to special-case it as an effect of rainstorms. While it's slightly useful then to have electrical conductivity to determine where the lightning is likely to hit, thermal conductivity is a decent approximation, for reasons I don't feel like explaining right now. Whereas once electrical conductivity is in, we'll be deluged with suggestions like the ones from when the 3D version was new and everyone went crazy over the material raws: "Hey, saltpeter is in! We can make gunpowder! And pitchblende--we can extract uranium! Hey, Toady, the game does simulate radiation poisoning, right? Can I build a nuclear bomb to use against the goblins?"
Rain provides no danger in the game, when it should be accompanied by lightning and Dwarves being ground-dwelling creatures should be at risk if they're not properly building their caves. Above-ground Dwarves should be at risk of their wooden forts being struck with lightning and burning to the ground. You know the real risks medieval societies faced.
The real risk from rain should be flooding, since you live in a hole in the ground. Hardly anyone builds aboveground wooden forts anyway--wood is too scarce for that.
"But you
can..." "But maybe you're playing some weird challenge game..." "But maybe you've modded the game to be Human Town and you have no miners..." But
in its basic, as-distributed form the game doesn't really support wooden forts as a construction style. So spending a hundred hours implementing another framerate-killing layer of physics simulation, so that someone playing a specific marginal strategy can have the satisfaction of watching it burn down in a physically realistic manner, doesn't seem like a great use of developer time.
People play challenge games, but the point of a challenge game is that the game isn't exactly designed for that. It's designed around its core concept, which is still (I'm pleased to note): Dwarves. They build a fortress.
The Power element as is is completely deniable in game. You can build a wooden fort in a serene area and live off of above ground farming and survive off of leather and crossbows. Or you can ignore the entire wood economy by digging deep and finding magma. A single Dwarf can move Magma up a pumpstack if you take the time and you could ignore perpetual motion in the same.
And yet it's in there because it's appropriate to the setting and concept of the game.
Right now, mechanical power can be used for only two things: pumps, which are extremely useful, and millstones, which are pointless. Toady has talked before about extending this to more kinds of machinery, like conveyor systems, elevators, and mechanized workshops. All of those
could be electrical but there's no reason they have to be. They can run on wind power or some guy turning a crank.
The machines that require electricity are the ones that are blatantly out of setting, like telephones and lasers. They don't belong in the game. The cleanest way to keep them out is to avoid anything electrical.