I do not know how a regular market is in your country, but in Nigeria, where I live, we have a regular market, and traders line themselves up in different batches to sell their goods and get money in return.
Walk into any Nigerian market, and you'll find dozens of traders selling identical products along the same stretch. Looking for rice or yams? You might see a hundred-meter line of competing vendors. Each trader fights fiercely for customers, sometimes literally competing for the same buyer's attention.
Fighting to get customers is one of the reasons enmity brews among these traders, and then you wonder why they do not come together to form a large business instead of staying separate, owning small shops and kiosks, and making little or no sales. If they come together to form a bigger business, they would make more sales, sell at a lower price, and divide profits after the sale.
Nigerians prefer to own 100% of a small business rather than to own a small percentage of a big one that would pay better. A lot of people have faced issues of fraudulent activities in their previous partnership, so it is very difficult for them to trust another partnership. This is why we have so many people starting small ventures, even when it can be difficult to make sales.
https://commons.wikimedia.org/wiki/File:Eastern_Boki_Market,_Wula,_Cross_River_State
Another reason why these people do not partner to form a bigger business is that they believe they are better at closing deals than the other person, and they do not want to be the one making the sales while the other person doesn't. Instead of working together, they feel they are being cheated and decide to manage their small venture alone.
Another reason why partnership is difficult with these sellers is deciding who calls the shots. They do not want to be inferior in their business; they want call the shots and so they do not want to partner with someone.
So which would you choose: full ownership of a small business with limited income, or a minority stake in a venture worth 100 times more?