The reason why the horizon never rises to eye level, regardless of how high we ascend on Earth, is due to the curvature of the planet. The Earth is a spherical object, and as you move away from the surface, the horizon appears to drop or recede from your line of sight.
The curvature of the Earth means that as you stand on the ground, the horizon is at eye level. However, as you ascend to higher altitudes, such as in an airplane or on a mountain, you increase your line of sight and can see farther in all directions. As a result, the horizon appears lower in your field of view.
This phenomenon is a consequence of the Earth's geometry. If the Earth were flat, the horizon would remain at eye level no matter how high you ascended. However, due to the Earth's curvature, the horizon gradually appears lower as you gain altitude.
It's important to note that the curvature of the Earth is not always immediately noticeable, especially at lower altitudes. However, as you increase your elevation, the curvature becomes more apparent, and the horizon appears to drop below eye level. This observation provides evidence for the Earth's sphericity.