Also known as plunging or indirect fire, this technique is intentionally used to accomplish a few goals.
1) Target Background When you use plunging fire, even if you miss, you won't hit something far off in the background. This can be used to prevent collateral damage.
2) Proximal Fire Projectiles that explode, such as artillery shells or classic fireballs, will impact and detonate near the target, if you only miss by a little bit. This can vastly increase your chances of a successful attack.
3) Armour Mitigation For armoured targets, plunging fire can often hit more lightly armoured overhead areas like turret tops or open decks. In certain fantastic scenarios, plunging fire will pierce a target that is supported by the ground, instead of knocking it backwards to arise unharmed. Compare hitting a hanging piñata from the side to hitting it with an over hand swing when it's on the ground.
4) Overcoming Intervening Terrain It may seem obvious, but it's worth mentioning for the sake of completeness that walls or other objects can be avoided in this way. This includes scenarios where your target is at a higher altitude than you.
5) Remaining Hidden May not apply to your specific scenario, but sometimes an attacker will want to take advantage of the intervening obstacles to remain hidden themselves while still being able to attack.
EDIT: 6) Preservation Of Velocity I had to think hard to remember this one. With indirect fire, your projectile will be driven by gravity to a velocity determined by altitude to a maximum of the projectile's terminal velocity. In certain circumstances, plunging fire may impact at a higher velocity than direct fire.
EDIT: 7) Ranging Where visual feedback is required to help zero in on a target, and the projectile is not visible (high-speed artillery shells, invisible magic force ball, etc.), indirect fire will impact somewhere near the target, allowing one to adjust their aim. Direct fire that misses will likely provide little to no visual feedback with such projectiles.