Why rotors instead of jet engines? Can that not be done? I’m just a fungus.....
A good question: jet engines work using the thrust of the engine itself to provide lift. It's inefficient, very sensitive to throttle settings and REALLY noisy. Rotors, on the other hand are more fuel-efficient, far less throttle position sensitive, much less noisy, and when well-engineered, handle transition between hovering and high-speed level flight much better that a pure lift jet engine, particularly in the thicker air of lower altitudes.
Rotors give downthrust without the heat.
It can be done but the problem is total lift = volume of air moved x velocity of the air.
A jet engine produces a smaller volume of air moving at a much, much higher velocity to generate the same amount of lift as a rotor (or propeller) moving a much larger volume of air at a slower velocity. When you land, have troops fast rope from a hovering aircraft to the ground, or sling a load under the aircraft, the lower velocity of air is much more desirable.
Also, at very low speeds and in a hover a rotor is much more efficient than a column of jet exhaust in creating lift.