It all comes down to the different interpretations of the artifacts
for example, up until late 20th century (sorry dont know exactly) barely any bodies were found in Herculaneum so it was believed that only the old, sick and poor died. However with 139 bodies excavated on the beachfront Estelle Lazar leads the way in arguing that the bodies represent a cross section of the society of a whole and not just the old and the sick.
Basically, just debate the interpretations of the evidence...