People like at least getting the feeling their report's being looked into. Without hearing something, it feels like it's ignored, especially if 0 consequences appear to be connected to the report from the reporter's perspective. This thing where the follow-up isn't shown to the reporter, is where the ''reporting to the email never works'' stereotype stems from.
I get the logistics problem, though. Especially since an unsatisfactory result will probably lead to more discussion between reporter and HQ, and a lot of the reports probably aren't that important from HQ's perspective.