I'm not going to lie the first few new server events were good but ever since then all the events after have been getting worse. It seems like the developers got some sort of an idea to start milking the game when probably seeing so many people buy the Jonin medal and spending here and there when new servers opened. To get as much money possible by creating very low chances of actually receiving anything good without spending money heavily. You know how in the beginning they were saying this game had a different VIP system, where in this game unlike the other Naruto web browser games people that didn't spend a lot of money still had chances to become strong and compete with spenders? Well it seems like they are doing the complete opposite now and increasing that gap. Becoming like every other naruto online web browser game that has came out. And this is coming from someone who pays 2 win. Even I see how unfair this game is slowly becoming.

So it takes less time to make a new event than to listen to people and improve those same events before releasing them in order to make them more fair for everyone to obtain the rewards?

You're right they don't have to have an event every week or every so often, but then again people don't have to play a game that is dead where there is no new content being released to make people want to keep playing it.