This clip is of a points karate match, not a full contact contest. Points karate prioritises speed over impact.
Pronounced bouncing is typically viewed as undesirable in full contact fights, because the rhythm created by the bouncing makes your strikes more predictable, and also allows your opponent to time strikes to land either when you're unweighted (and therefore easier to unbalance), or fully-weighted on the downward, landing, phase (and therefore unable to counter or check when defending a leg kick, for example).
With the exception of certain strikes such as flying knees and kicks which utilise the power of leaps, or the gravitational force of a descending body or limb, most basic techniques are rendered more powerful when launched off a solid base (ie: bodyweight anchored firmly to the ground via one or two legs).
Much of the power generated by punches rises from the feet, to be amplified by the legs, then again by the hips, the shoulders and arms. A kick such as a roundhouse or a front kick also transfers far more energy into an opponent if the opposite leg remains in contact with the ground. Without this contact, some of the energy gets wasted; it is redirected back into the attacker, sometimes manifesting as undesirable loss of posture, balance, offensive and defensive capacity.
See this clip of a Kyokushin tournament. Yes, they still bounce slightly, but just enough to maintain motion; to avoid a static stance and promote explosivity. The reduced bounce means it is easier for them to ground themselves quickly prior to executing a technique when they need to.