VTOL engines must be heavier than traditional engines because they need to produce sufficient thrust to counteract gravity without the benefit of forward speed and wing lift during takeoff. In a conventional takeoff, the aircraft accelerates down a runway, allowing the wings to generate lift that overcomes weight, while in VTOL, thrust is directed vertically, requiring the engines to provide all the lift initially. The thrust-to-weight ratio can be less than one in traditional aircraft because wings generate lift, while in VTOL, the engines must continuously provide thrust until the aircraft gains altitude. The discussion also highlights that drag is not the primary concern during VTOL takeoff, as the immediate need is to counteract gravity. Understanding these principles is crucial for pilot training and aerodynamics comprehension.