There's research that has shown that stress in the early years of life delays development of the hippocampus - and without sufficiently developed hippocampus you can't have these kinds of memories.

So the generalization ("all kids") is wrong, but some people, being exposed to toxins or stress sources (fetal alcohol syndrome, cigarettes, lead, premature birth, asthma, ...), can really only develop memories later. 10 years is a bit much, though...