Think of it this way, a scam report must be thoroughly investigated before any action is taken. A spam report does not need to be, and can be handled rather quickly.
If the staff member wants to dedicate time to doing something such as scam reports, it would be more effective for them to visit the forum rather than see a post in the IRC. However, if the report a spammer section is empty, and the second a report is filed it's posted in the IRC, staff monitoring the IRC can easily and quickly take care of it.
Thus, reports are handled almost instantaneously.
Something that cannot be done with scam reports

.