Why is a just a rather odd wh -word. Its distribution is very limited -- it can only have the word reason as its antecedent, and since it's never the subject it's always deletable. Consequently it behaves strangely, as you and others point out.
Does this "should" have some special meaning? For young professionals, why should they want to work in a large commercial bank? What difference is there from just using "do"? ...