I agree, an empty belt isnt of much use. I leave most of my belts loaded, some have been for 30 years or more. They get cruddy, I clean them off a couple times a year, some maybe once a year, or first of the season I take a belt out if it isn't a daily user. I wipe the rounds clean with a rag and use a nylon bore brush of a smaller caliber to gently clean the inside of the loops out. Nickel shells are OK, but not always as easy to get. I also use nickel in some, like 45 Colt and 45-70 as an easy ID for the heavier loads, so the others in the belt are not all going to be the extra heavy ones.
Some do it more than others. The way the leather was tanned or treated makes a difference, but I don't think Ive seen any that never ever got some verdigris over time.
I don't agree that cartridge loops weren't around much until movie days. Individuals and saddlers in the military started adding loops to plain military pistol belts in the 1860s and it took off from there. No, they weren't the heavy leather so much, but cartridge belts were certainly around. Soft leather, doubled over was common, they were sometimes called money belts, coins or papers could be slid into the end of the belt. The book
Packing Iron has some good history with many excellent pictures, as do some of the earliest films. Look, at their rigs, they aren't "Hollywood" fast draw style belts with the holsters hanging off a loop on the side of the belt, they are plain, old time cartridge belts, some with loops torn loose, the well worn working gear of the guys they got to play cowboy extras in the early days, not professional actors or people outfitted with prop gear. Museums have plenty of old leather, as do real period photos. Cartridge belts are generally commonly seen. Many wore them with the loops on the front, I have at times, its much easier to reach the loads if hunting or its cold and wearing a coat that restricts movement.
The cavalry issued cartridge belts for rifle cartridges in the 70s, and buffalo hunters used them commonly. Ive seen what looked like a handmade one in the Winchester Museum made for 50-70 cartridges and used with a Sharps full military rifle, used as a buffalo rifle which I believe was a cartridge conversion, something done quite a lot by both individual gunsmiths, and the Sharps factory several years before the 1874 model came out. I think many people tend to have tunnel vision of the old west from watching too many western films, there were far more types of people in the west than just cowboys, who may or may not be able to afford a pistol or even a carbine, and some outfits even restricting carry. That may have worked in Texas, but not in the mountain and plains country of the northern states. Many of what may be considered frontier types wouldnt consider going out without a rifle at least, some of those people lived from their guns for food, and protection during the Indian wars period as well as outlaws. Some may have punched cows part time, or in later years. Many in earlier times were trappers, wolfers, buffalo hunters, prospectors, woodcutters for the riverboats, freighters, teamsters, scouts for the military, meat hunters, and all manner of wild types. As various gold fields opened, there also flowed the hopeful ones, and the dregs that preyed upon them.
Cartridge belts aren't as common, or perhaps not as commonly used today, but they still are a very handy and relatively compact way to have accessible ammo for your gun. I keep a belt of 30-30 cartridges with my carbine in my truck, another hanging by the door, and several boxes of ammo close by with each for spares. Same for my most used pistols. I walk every day some. I like being able to grab the belt rig for the pistol, and/or the belt for the carbine on the way out the door, to walk, go to town, or whatever. I keep a few light loads for skunks, snakes or grouse, as well as regular full power loads in the belts.
Ive had this belt since about 82 or 83. Its been loaded since I got it. It was a 44, but eventually stretched out enough that it became a 45 colt belt. Its ben restitched 2 or 3 times. For a cheap belt its held up fairly well. The holster is only a few years old, it hasn't acquired much character yet.