Tandas / ROSCAs are useful savings vehicles when it is, for whatever reason, difficult to hold on to money for very long. There's the physical version of this (The local warlord regularly mirks people for their wallets; Or maybe your government has something called 'civil asset forfeiture'), the social version ("The husband with shared access to my accounts drinks it all away!") but also the investment / monetary version where you have limited legal investment opportunities ('Peasants aren't allowed in the stock market'), or you have hyperinflation and so have to deal with the complication of a constantly shifting dollar. The money doesn't need to dwell any place for long periods of time, it's collected and distributed and then _spent_ on an expensive non-divisible improvement to your life immediately.
I play a survival game called Rust. Progress is meted out through the slow accumulation of Scrap, which is spent on learning technologies. People constantly kill each other, and those who are ahead on tech tend to accrue advantages in combat. There is no "Bank", and no guarantee of the ability to set up a minimum viable base to store your resources. One of the most pathetic strategies to resort to on the busiest most crowded servers, when you're a few days behind, is to linger around the edges of a safe zone collecting small amounts of Scrap(dying every few minutes), literally play roulette with it at the in-game gambling system in the safe zone at 1:20 odds, and when you eventually win big, use your scrap to progress through the tech tree; It might be 1000 scrap to get your tech to where it needs to be to compete, and you might average 50 (w/ Std dev of 25) scrap between deaths, but you'll get there eventually in this way, whereas the non-gambler needs incredible luck (+38 standard deviations of success) to actually progress through this high price threshold.
A typical tanda removes the random chance element, but preserves the "Eventually you'll get there" element even while holding on to no money.
I play a survival game called Rust. Progress is meted out through the slow accumulation of Scrap, which is spent on learning technologies. People constantly kill each other, and those who are ahead on tech tend to accrue advantages in combat. There is no "Bank", and no guarantee of the ability to set up a minimum viable base to store your resources. One of the most pathetic strategies to resort to on the busiest most crowded servers, when you're a few days behind, is to linger around the edges of a safe zone collecting small amounts of Scrap(dying every few minutes), literally play roulette with it at the in-game gambling system in the safe zone at 1:20 odds, and when you eventually win big, use your scrap to progress through the tech tree; It might be 1000 scrap to get your tech to where it needs to be to compete, and you might average 50 (w/ Std dev of 25) scrap between deaths, but you'll get there eventually in this way, whereas the non-gambler needs incredible luck (+38 standard deviations of success) to actually progress through this high price threshold.
A typical tanda removes the random chance element, but preserves the "Eventually you'll get there" element even while holding on to no money.