Why is the process of staging necessary for a launch vehicle ascent?

To shed dead weight like empty fuel tanks and spent engines.

Staging is an essential concept in rocketry employed to maximize efficiency during ascent. A launch vehicle carries a massive amount of propellant and engines that are only needed for specific parts of the flight profile. Carrying these empty or spent components further into the flight, especially toward orbit, is incredibly inefficient due to the physics of needing to accelerate dead weight. By shedding these parts—empty fuel tanks and spent engines—the remaining vehicle mass is significantly reduced. This reduction in mass allows the subsequent stages to achieve higher velocities with the remaining fuel, making the overall mission to reach the necessary orbital insertion altitude and velocity far more achievable and fuel-efficient. This controlled abandonment ensures that only actively needed hardware contributes to the acceleration toward space.