TV and film actors get them because the the lighting on set makes your teeth semi transparent and they look like shit on film. They tend to go overboard with them and they don't look natural. Plus once they get them, they always have their mouths hanging open because their teeth don't fit anymore, see above pic I linked to.

Her massive veneers have always made me laugh. She can barely close her lips around them, and when she does she looks like a boxer with his mouthpiece in.