I just finished reading The Recollections of Rifleman Harris today, a memoir by a British soldier in Portugal & Spain during the Napoleonic Wars. They (try to) loot very often as you might expect, are constantly surrounded by corpses, but still never have anything good in their inventory.
1. Enemies know they'll be searched and hide their money. The only time he gets actual money off a dead guy, he found nothing at first. Someone experienced comes by who tells him to check certain spots and he eventually finds the dead guy's coins in a secret pocket in the lining of his coat. His own money is in his hometown bank and whenever they get any pay they usually spend it right there or send it home via the logistics chain.
2. His inventory gets dumped very often to lighten the load during marches. Marches are always brutal and sometimes the dudes even throw their weapons away. One time he and a buddy drop from exhaustion and wake up at night. They get lost in a swamp and nearly drown, lose most of their gear and only survive because the officers send dudes out with lanterns to collect stragglers and they crawl towards the light. By the time he leaves Spain, he doesn't even have a backpack because it got too heavy to carry so he dumped it and the only reason he kept his rifle is to use it as a walking staff. Even his belt and bayonet scabbard fall into the sea when he's climbing onto the ship to go back home because they get tangled and he'd rather leave them than fall and drown to save them.
3. Things, especially clothing, are very poor quality to begin with. It all falls apart because it's cheap, especially footwear. There are no left and right shoes, only square toes, with small, medium or large as the only sizes. Most of the time the only real loot is taking boots or shoes off dead guys that are only slightly better than yours. Most of the longer marches end with even the officers wearing rags on their feet because even their expensive boots have literally fallen apart. Even the hats are poor quality. By the time they arrive back home most of the dudes are wearing bandana rags on their heads.
4. The stuff that doesn't fall apart, the soldiers destroy themselves. At one point everyone takes the metal buttons off their tunics and bend or beat them into coin shapes, pretending they are British money to buy wine from the locals. They literally drank their buttons away....
5. He finds the biggest loot trove ever in a hat lying beside a dying guy, who is clearly in a lot of pain and suffering badly. The hat is full of golden/jewelled crosses and other obvious church loot. He's too scared to take anything and thinks the French guy is dying horribly as a curse for having looted churches. This also comes up when he's thinking of looting his own guys. One of the British officers dies and he'd love to take his boots, but the others are watching and he doesn't want to get in trouble for looting his own dudes.
6. They're constantly hungry. The best loot is the kind you can eat. Looting raw turnips in the field? Check. At one point he's so hungry he takes a half chewed biscuit hanging out of a dead guy's mouth, wipes the blood off and eats the rest.
7. Local people literally buy anything if they're trading. At one point he sells the shirt off his back for food, but the trick is he doesn't usually come across local people...most of the time they're either hiding or don't want to interact because they're not sure if the French will win and then they'll be in trouble.