Why sell calls?

I guess I should probably clarify a bit. From what I could see of my rookie partner last night, he wasn't trying to showboat. You could tell he was working on the mechanics of the sell safe or sell out call. I just felt he was using the wrong tone for the situation at hand. I told him that the closer the play, the harder the call. I was hoping that would help, but it really didn't. I don't know how else to explain the idea to him. Ideas?