Why Jump?

It strikes me how often this comes up. I was playing a friend's RPG, during which I engaged in a mech battle arena. Somehow, jumping came up, and he asked "Why? Why jump when you can fly"? In fact, there a number of reasons.

1. Jumping is quicker. Often, jumping in a mech will have a greater high speed than flight in a mech. However, even in DBZ-like scenarios, flight will always involve acceleration. The acceleration in jumping involves mainly the few seconds touching the ground; in the air, the character will stay at pretty much the same speed.
2. Jumping is more silent and harder to detect. In the mech scenario, the initation of boosters of most kinds will generate a visisble light flash (a sore thumb to thermo-imaging and light amplification), heat, and noise. Even gravity flight will be detectable by potential gravity-anomaly detection techniques or by a whirring sound. However, gravity is usually used like a "jump" (M-308 Gunner), so it backs me up. DBZ characters also are more visible during flight. Most generate some sort of aura around them when they fly; even the Super Saiyans get a visible boost in aura size during flight. And, flight tips off Scouters and the natural clairvoyance of the DBZ fighters much more than jumping. Even tDr. Gero, undetectable by the Z fighters, uses jumping and running instead of flying because it would make him visible.
3. Jumping costs less energy. When using a jet pack or boosters, you have a limited fuel capacity. Continual use will deplete that capacity. But you can jump as long as necessary; unless your legs die out or you become tired, you will be fine. By this logic, using limited flight and booster-assisted leaps appears to be a better idea. Which brings me to my next point.
4. Jumping can be combined with flight to avoid many of the problems observed here. By jumping, you may get a literal "jump-start" and avoid acceleration difficulties. The problem of being more visible is reduced. And you can conserve energy.
5. Jumping offers a very good attack tactic. Flying at the ground at maximum speed could kill the character. But by using Jump in the Dragoon Style, you can avoid the problem and still get a very good velocity.