First, this comes across as just another pain-in-the-■■■ mechanic that people are going to complain about. Nobody is going to want corruption fields in their bases.
Second, the obelisks in game, as far as I remember from reading, were given corruption auras because jerks were camping at them and griefing people when they were teleporting to them.
Third, the Map Room and Obelisks in game work with the bracelets to teleport you. They were designed to teleport useful slaves from one point to another within the Exiled Lands. Adding a corruption requirement now would mean that every slave then would have to have been some type of sorcery.
Making it sound as if sorcery is so commonplace that everyone has access to it. Which doesn’t make sense.
The Map Room and Obelisks were a tool, they functioned on their own, without any direct need from the slaves that were being transported. So applying a corruption “requirement” for that wouldn’t make sense.
It’s essentially the same thing as saying someone in the real world needs a special power to whack something with a hammer, or pull a trigger to fire a gun, or to be able to understand how to turn on a television or radio.