Also
If we take a single move from an old form, it has hundreds of applications.
However if we only train the move in application we will only train one or two of these applications.
By training the movement in form we gradually start to realise the 'PRINCIPLE OF MOVEMENT' we start to learn the formula behind the technique. Once we have this we can dispose of form entirely and rely on the principles of kung fu to fight with.
If you only ever train the specific applications of moves it is harder to learn these underlying principles.
By training form you can unlock these principles and move from form to formlessness in combat. However going straight to formlessness is not so easy.
NOt saying form can be trained alon and make you a good fighter, but it does help as part of your training and i think it should be trained along with sparring and striking and all the rest.