It's not about scaring off anybody or discouraging the hobby.
Like most certification tests, its serves as proof that you've seen the right way to do something at least once. Like when you got your driver's license, you proved that you knew how to fully stop at a stop sign, signal before turning, and obey the speed limit. Then when an officer gives you a ticket for those things or you cause an accident, "nobody ever told me" is not a valid defense.
So going forward, when some goober causes a commercial plane to have to be rerouted or violates someone's privacy or injures someone, there will be no excuses. And if a drone pilot is bothering someone and the police are called, they have a concrete thing to check for. No certification=you broke the law.