I might be wrong, but I would think that a full suit of armor would be expensive, as would the horse barding and weapons that are conveniently all gathered in a large area, albeit in possibly poor condition. While I'm aware that small scale scavenging after a battle can and did take place, did the victorious side in the engagement ever make any effort to strip the bodies of valuables? Did they just send in everyone, or were there small groups of people who did this regularly?
So yes they did but it was usually the camp followers, washer women and squires that did this.
Medieval Armies were really more like traveling mobs of people than the straight marching, orderly processions that appear in movies. No Medieval King in Europe had the money to maintain a large standing army. Small forces for castle defense and tax collection could be maintained but in times of war a Medieval Army was conscripted from various groups of former soldiers, mercenaries, bandits and unbound knights. This was all fine but the King really had very limited control of these people outside of actual battle. As a result the conscripted soldiers/knights brought a bewildering retinue of people with them on campaign: wives, mistresses, children, relatives, squires, fortune tellers. All these people were just called 'Camp Followers" and like the name sounds they just followed the main army at a distance.
After the battle those fighting in it were totally exhausted physically. They had just done hours of intense physical activity while wearing 60 to 120 pounds of gear. While they were passed out the cam followers of the winning side would roll in and strip the opposing dead of anything of value. This looting would go on until dark and was very common. Some kings like Henry V, specifically banned his forces from looting during or after the battle but this was the exception and not the rule.