The reason being that there are no other more logical places it will be seen.
Moreover, anyone wanting too sell or find re-loading kit knows where to look.
Like you say, not a lot of folk paying attention, particularly as the link to the post is doing it's job, re-loaders are still seeing the link "in the re-loading section" and following it.
All in all a great way of self burdening by the mods while those posting sales or wanted in the most logical place still get the desired effect.
Yarp...well thought through