Who said anything about wires? The etheric currents flow all through the spire. Folly comments on places where there's a strong current once or twice. I'd say the crystals draw energy directly from that. As far as stealing crystals, I doubt it would be a huge problem. You don't see many people stealing street lights in our world.
1) Sorry. I meant "wire up".
2) People might not steal street lights these days but that's mainly because there are other things that are worth more and easier to steal. Note for example that stealing copper (from telephone wires) is still strong. They actually put together a special
task force to deal with it. Thus, I submit that given the worth of lighting crystals, people will inevitably steal them.
3) Doubly so for deliberate sabotage as a form of warfare.