The role of pushing hands

Pushing hands can be seen as a form of grappling.
Having made contact with an opponent, you are essentially pushing hands.

At this point, you can employ any of the three main areas of skill in order to incapacitate the attacker:

1. Shuai jiao (grappling)
2. Chin na (seizing)
3. Jing (energy expression)

Pushing hands fills the gap between an attack being launched and the defender finishing off the opponent.
It is not and end in itself and cannot realistically be used in combat.