I don’t understand? – Mercari: Buying & Selling App Review

How do you not get scammed when you’re selling something but don’t receive the money until after the customer has confirmed they received it? What if they never confirm it even if they received it? Couldn’t they easily say they didn’t receive the item and get their money back? Like am I just supposed to trust that people aren’t dishonest scam artists???
Review by Briannanaia on Mercari: Buying & Selling App.