As the player base grew, those stickers became more rare and thus more popular (especially the Holo versions). The very first stickers that were available in CS:GO (Katowice 2014) were only bought by a limited amount of people. These things result in the amount of available stickers that have not been applied to guns going down. Some people are also curious of what stickers look like when they are partially scratched. Stickers also often get scratched off (destroyed) because people have different tastes in colors and teams. You can buy a sticker for less than a dollar, and there is a large community that slaps stickers onto their guns because they look nice. The nice thing about stickers is that they are relatively cheap, limited in supply, and get destroyed at a relatively fast pace. The problem with things like this is that skin prices are hard to predict, so you need to be able to get them at a discount if you want to make a profit. For example, I once bought a M4 Howl Factory New from a 3rd party website for about $600 and resold it within a week for a nice profit. I have done a version of this and was very successful, but it has become harder now since more people have figured out the system.

You can try to buy regular CS:GO skins and resell them at a later date if they go up in price.

How to get cs go stickers