again where is your support that any of this is "lore" based???
Apples and oranges since the mechanical rules for both apply equally and only the stresses are different as I understand things.
the principles are the same, but the needs are very different. you would not build a quarter mile tall building without giving it grounded support would you? how about an embedded lightning rod, would you use twigs or metal and concrete?
you should get the point right... about...
now.
you could justify this in a zillion ways, that the atmosphere depletes shield generation, that you dont have a sufficient view of the sphere over earth to project from the surface, you could claim that the distance from the emitters to the shields would be an issue, or that convexity of the energy shield at such a distance would be impossibly unstable, maybe you need a more accurate system so that you aren't blocking your own gravity elevators from working etc. etc.