People complain about it because they unrealistically expect SE to immediately act on every report and nuke the suspected RMT/botter as soon as they register it. Because this takes time though, they're not satisfied with this. Unfortunately, it does take time because they have to investigate each report to check it's not a mistake or someone trying to use it as a form of harassment on another player (like framing someone for a crime). Due process has to be followed naturally.