Poorer parts of the world also purchase a LOT more products packaged in single use packaging than industrialized countries. In the Philippines, pretty much every consumer product that could be sold in a multi-use jar, tube, or bottle instead comes in a single-use plastic sachet like you would get for ketchup in McDonald's. Laundry detergent, toothpaste, hair products, you name it. When you combine that with a lack of waste collection infrastructure, you end up with the Pasig river full of single-use plastic sachets every time it rains.
Here's a well researched report that dives into a lot of the issues of why these plastics are used. It is a combination of economic and societal factors.
https://www.no-burn.org/wp-content/uploads/2021/11/Sachet-Ec...
And here's a article that names and shames which companies produce most of the single use plastic waste found in the Philippines.
https://www.rappler.com/environment/findings-philippines-pla...
https://www.newsecuritybeat.org/2020/09/turning-tap-plastic-...