Why were the Triarii differently equipped?

[Corvus]

Steven has cited the evidence that he believes supports his case. Now I think it only reasonable to ask that those who take the contrary view cite the evidence that supports theirs.

The most examples he quoted, are examples from time of an emergency.
It makes sense, that the population, that is not supposed to do service in the legions , gets armed in a time of an emergency, when the city is at danger.
besides that, we cant trust what Livius writes to 100% and need be critical, because he is not a primary source.