I think you misunderstood what I meant.
Let's assume there's 36° between the -3dB axis on each side of your lobe, on the vertical plane.
At a distance d, the vertical distance h between those two -3dB axis is still 36°, so h = d*tan(36/2).
Unless I've screwed up my calculations as I often do, at 1m, that's 30cm high. At 100m, it's 32m, and at 1km it's 325m. So, unless your target is more than 325m above or below you, at 1km you are ALWAYS in the -3dB lobe.
Conversely, if your objective is to cover a wide area, using an antenna with a lesser gain (relatively to an isotropic antenna) will make you radiate a lot of energy toward the sky and the ground.
To make an analogy with light: many streetlights are big, round globes illuminating equivalently all around them. You could see them as low gain antennas. They also illuminate straight up, which is completely useless, because it's the ground to want to see. Now, there are also streetlights that are pointed toward the ground - and with the same energy, they will provide more useful illumination than the omnidirectional streetlights.