I believe that it is pure causeless mercy of the Supreme Lord that we can't remember our past life experiences.
We can't handle the traumatic situations of this one life; what to speak of countless other previous lives?
Anyways in Srimad Bhagavatam Lord kapila explains how the child loses one's memory when he comes out of the womb of mother.
this is explained in third canto of Bhagavatam; Chapter 31
Pushed downward all of a sudden by the wind, the child comes out with great trouble, head downward, breathless and deprived of memory due to severe agony.
in commentary A.C. Bhaktivedanta Swami Prabhupada writes.
When the child comes out of the abdomen through the narrow passage, due to pressure there the breathing system completely stops, and due to agony the child loses his memory.
the next verse(3.31.24) says
The child thus falls on the ground, smeared with stool and blood, and plays just like a worm germinated from the stool. He loses his superior knowledge and cries under the spell of māyā.
Note:Also I'am not sure if dog remembers their past life. However I dont think so.For there are no strong evidences in its support.