Why 1–2–low kick is the most-drilled sequence in the sport
It is not tradition and it is not habit. The cross leaves your body in exactly the position the rear low kick launches from, so the kick costs nothing to add.
Walk into any Dutch-influenced gym and you will hear the same sequence called more than any other. There is a mechanical reason for it.
Throw a cross and the rear hip rotates forward while weight transfers onto the lead leg. That is precisely the starting position of a rear low kick. The rotation is already happening; the kick continues it rather than starting a new one. Add the kick and you pay no setup cost, no repositioning and almost no extra time.
The combination also builds its own opening. Hands at head level force the guard up and pull the opponent's weight forward, and a leg carrying weight cannot be lifted to check. The punches are not a distraction — they are the mechanism that loads the target.
The general rule this illustrates is worth more than the specific sequence: consecutive strikes should either continue a rotation or deliberately reverse it with a step that resets the hips. Left hook into right low kick works. Right cross into right head kick works. Right cross into right cross does not, which is why doubling the rear hand needs a small step to be anything other than slow.
Elite fighters use very few combinations. They use a handful, from both stances, against several reactions, at a speed that makes the decision invisible. That invisibility is the entire purpose of the Dutch pad round.