The bow stance requires focus, determination and movement. While it is possible to fight from a (correct) horse stance without moving, a bow stance needs to focus something into the hand techniques. The back leg has to be driving forward into the hand techniques. The front leg provides stability and directional capacity. Without shifting forward or stepping, the bow stance is wasted. Even Throws require movement to properly use the bow stance. In any style which moves forward in a focused effective manner, the bow stance is a necessary fighting tool. By effective I mean that the opponent hasn't retreated and left space available; therefore the attacker must move forward into a contested location without being knocked aside or stopped outright.
In nearly every confrontation without a decent bow stance, the opponents hop around out of range and lean into range to throw techniques as quickly as possible before retreating out of range. After boredom sets in, one of the combatants decides to take a strike in order to get into better range for their attacks. After the Bruiser fest sets in, a solid hit occurs and one guy goes down or panic sets in and grappling occurs.
The bow stance is supposed to remove boredom, panic, and confusion from a fight. It imparts control, power, and technique to a fighter. One good step into a bow stance can traverse all ranges of combat and devastate the opponent. It is the most effective entering stance taught by any style. By this, I mean an active decision to attack as opposed to defending in the hope of a weakness or luck allowing a counter. The fact that nearly every art has countless counters to bow stance attacks should be an example of its effectiveness, just like clothes have not made weather obsolete.
The bow stance is used in most chi kungs and is the first stance kicks are learned from. It is often taught before the first form, or the first moving form.