Why don't helicopters always takeoff from a hover out of ground-effect?
Forward flight is much more efficient than hovering.  As airspeed builds, lift increases from "translational" lift as the air moves more horizontally over the disc.  Since the relative airflow is more horizontal, the angle of attack for a given pitch angle is increased.

The vortices and turbulence move behind and down from the helicopter so undisturbed air is drawn over the disc to be accelerated downwards to produce lift.  Lift is more efficiently produced by accelerating a large mass by a small amount rather than a small mass by a large amount.

It is more efficient to remain in ground effect and slowly increase speed to gain translational lift than to increase power to HOGE (Hover Out of Ground Effect) and attempt to translate.

The problems you refer to are where an unwary pilot attempts to transition from HOGE whilst allowing the aircraft to climb or attempting to maintain height.  Without enough power, the loss of ground effect before the benefits of translational lift are gained will result in a rapid descent back to earth (as vortex ring state or settling with power is pretty much impossible to avoid) or you overpitch and drag the RRPM (rotor RPM) down so low that you cannot produce lift or even worse, stall the blades.

Bottom line, it takes more power to establish positive climb out of ground effect than to gain translational lift in ground effect.