And just like drawing water from the air If you use the right materials it can be extremely effective
Sorry, to be more specific, you can't go from a lower state of energy to a higher state of energy without adding energy. The energy to do that has to come from somewhere. Simplest example is a rock at the bottom of a hill can't get to the top of the hill without energy being added to it. Once at the top of the hill, it can discharge its energy by rolling back to the bottom. Likewise with electricity in the air. It is there, but it is all dispersed already. In other for it to become flowing current, you need to have it flow from a point of higher concentration of electrons to a point of lower concentration of electrons. Since all the electrons are equally dispersed, the only way to do that is to bunch up all the electrons into some space that will end up with a higher concentration of them than the surrounding space. That needs energy, either used to create static friction, a magnetic field that pulls them all together. It's kind of like being under water in a lake and trying to get water to flow through a pipe. Sure, there is water all around you, and your pipe will be full of it too, but unless you use some energy to push the water through your pipe, all that water is useless for doing work.