The matching of buyers and sellers is a hard problem. When there's a limit order book, meaning bid and ask resting orders on NYSE, by definition the buyers and

The matching of buyers and sellers is a hard problem. When there's a limit order book, meaning bid and ask resting orders on NYSE, by definition the buyers and sells can't be matched. To "match buyers and sellers", one needs to buy from someone at time T, and hope to sell to someone else at time >T, during which time the market could have gone up or down. It's a risk-taking processes and a problem that's underappreciated by those who never actually tried to look at the basics of how an exchange works. Also the best bid and offers on exchanges are often already market makers. To say you "don't need" market makers because of liquidity is a bit circular.