Board Thread:Manga/@comment-3568954-20150810140746/@comment-4929778-20151230162258

GodKingReiss wrote: The Royal Government had a ban on advanced technology for the past 107 years, so the Survey Corps must not have thought about it. But since the idea was brought up back at the start of the Uprising Arc, it could very well be a possibility in the Survey Corps's future.

The Royal gov never had a ban. If they had a ban, everybody would know. But as Sanes explains, it was all done in secret. It's like anthem, where no tech gets changed and nobody's gonna question because people know if they do, they'll get murdered and have it made to look like an accident.