Why Is a High Transaction Confirmation Time Sometimes a Security Feature?

A longer confirmation time, such as Bitcoin's 10-minute block time, increases the time and computational work required for an attacker to create a longer, fraudulent chain. Each block added to the chain exponentially increases the work needed to reverse a transaction, thus increasing the cost and risk for the attacker.

While inconvenient for fast payments, this slower rate provides a higher degree of probabilistic finality sooner, making large-scale attacks less economically viable.