Why most warships do not embark four mixed helicopters

Why are modern warships not designed for two medium and two light helicopters?

The space, personnel, maintenance, and duplicate logistics burden is too large for most surface combatants.

Four aircraft would already consume substantial flight-deck and hangar volume. Mixing medium- and light-lift types adds separate logistics, training, maintenance, and crew requirements rather than merely adding airframes. Every spare, maintainer, and support space competes with the ship's other weapons and missions. The apparent multi-role gain must therefore be weighed against a large permanent loss of ship space and manpower.