Why sell calls?

I agree with what's been said so far on this topic. But there's one more thing I would like to throw out there for discussion. Does it make an umpire look "foolish" or unprofessional for "overselling" a call? I worked with a fellow blue last night (a rookie) for the third time this season already, and he continues to oversell some calls (at least in my opinion).

What I mean is...doing a sell "out" call when it was an obvious out. Or doing the safe sell call when the ball never got thrown over to the base. In my eyes, overselling brings attention to umpires that is unnecessary. What's the feeling out there?