Not by what I've read - AFAIK armour came back in fashion later on. The bigger issue was probably just the damn peltasts and their javelins; I've read those things are *very* good at going through things like shields and armour, and it's obviously tactically somewhat unviable to stand there in nice ordered ranks in nifty expensive armour if a bunch of beggars with javelins whom you cannot catch due to the bulk of your gear cheerfully murder you despite it.