Why doesn't Rigidbody.velocity.x = 0 in a collision?

Questions & Answers
1

For context, I am trying to implement a parallax effect. The parallax effect is contingent upon my player’s 2d movement. When he moves, the backgrounds move at a fraction of the player’s velocity.
The player’s velocity.x is modified through AddForce functions (impulse).
However, when the player its a boxCollider2D, even though he is not moving in the scene, his velocity is still apparently non-zero. Why is this?

And if it is impossible to use Rigidbody2D.velocity to get what I need for parallax, what other methods can I use to get the player’s “true” in game speed.

2

There is only 1 situation in which a collision will result in velocity = 0 and that is a perfect head on collision with a totally non-moving object and only for the moment of impact. If the other object is movable then any imbalance, rotation etc will result in at least 1 axis retaining some velocity. If you really want it to be 0 on impact then you can script it to do that in the OnCollisionEnter routine.