Why does Kibum need 表演 lessons?

Well, I know that Kibum really wants to act but why does he need to undergo 表演 lessons? He's good already. I dont know if Siwon took 表演 lessons but he already got a lead role in a drama. Cant Kibum do the same thing? 或者 Siwon is just a better actor than him? I'm really confused.

I also conclude that if Kibum will not be 给 表演 lessons he might also do what Hangeng did, terminate his contract with SM. Because we all know that he (Kibum)just joined the company to act.

How about you,what do 你 think?