EGKB: Think back to when your instructor was teaching you how to do forced landings. Here, elevator definately has to be used to control airspeed since power (by definition is not available) So, ingraining this connection is a safe basic technique which can ALWAYS be applied. Now, fast forward to circuit work and now you are adding power to achieve a desired glidepath angle to land.
As many others have pointed out, other techniques also work but in the early days the elevator/speed connection is the easiest consistant way to go to cover normal + forced landings.