From our point of view, we need sleight of hand to be a magician. From the laymen's perspective, it doesn't matter because the magician does the sleight of hand alone. Only the magician knows how it's done and when the magician finishes his performance and the audience is very impressed with the performance, then the magician may feel 'guilty' and tries to sell what he is doing by saying "it's just a sleight of hand". It's very sad when a magician tries to diminish the effect of the magic by saying " it's just a magic trick". So I looked at Oxford dictionary and the definition of magic is as follows:- "The power of apparently influencing events by using mysterious or supernatural forces." Sleight of hand doesn't sound like mysterious to me. This expression actually reinforces the idea, " I will do something when you are not looking.All I am doing and magic is all about deception." This mentality is one of the reasons why magic isn't taken seriously as an art like acting and music. Remeber whenever you say, " it's just a sleight of hand.", you aren't doing magic. You are just doing 'something', when they aren't watching.