Why different coins need different numbers of confirmations

One chain releases funds after one confirmation, another waits for a dozen. The difference is how much work it takes to rewrite recent history.

What a confirmation is

Each new block makes reversing an earlier transaction harder, because an attacker would have to redo that block and every one after it.

Why the number varies

• Block time. A chain with two second blocks needs many more blocks to equal the same elapsed security as one with ten minute blocks.
• How much work secures it. A chain with less hashing power or stake behind it is cheaper to attack, so more confirmations are wanted.
• Finality. Some chains reach a point where a block cannot be reverted at all, and waiting past it adds nothing.

What this means

Waiting is not an exchange being slow. It is the cost of being reasonably sure the deposit will not disappear. The threshold is set by the chain's properties, not by preference.