On-chain lottery and scratch games are decentralized gaming applications built on a blockchain network. These games allow users to participate in a trustless and transparent environment, where the game results are determined by smart contracts and recorded on the blockchain. By using blockchain technology, on-chain lottery and scratch games eliminate the need for intermediaries and ensure that the games are provably fair. Players can trust that the games are not rigged or manipulated, and the payout system is automated, making it quick and secure. Moreover, the use of cryptocurrencies as the primary payment method enables players from all over the world to participate in the games without being limited by geographical boundaries or financial institutions.
This kind of lottery as you mention is probably fair, and we can verify their fairness in the smart contract, all good at that point, but talking about a decentralized project, I'm not totally sure about that for the next two factors... 1.- Someone has to put the money in the lottery to make it attractive to the users and 2.- Someone is winning money each time a user buys a ticket, and that profit hasn't to be direct profit, I mean, they can profit with the fees on that transaction if it's in their own token, or by bumping the token price in the market.