In the JP wiki, maybe in comment section, people have already pointed this out. But you have to remember, DMM need to make money, so if duping people helps them earn another 3% in profits, it's still better than them not having to try this. Events are just a way for DMM to get players excited about something that isn't anything that's worth bothering. Kanpani Girls suffers from the same issues, and events tend to be when they rake in the bucks from RMT.