There's actually many benefits to using a crypto marketplace over a fiat marketplace. Not that much for physical products, but for virtual products it goes hand in hand. A few examples:

1) When buying a virtual product for fiat you oftentimes need to wait for the payment to be processed, then be subjected to KYC because the item is fraud-sensitive and paying in fiat is reversible. It's a hassle to make the purchase, whereas with crypto you completely bypass the need for either by simply paying in non-reversible cryptocurrencies.

2) In the same vein, there's many virtual items you are unable to buy on Amazon and/or eBay because they're so fraud-sensitive. Anything ranging from gift cards, subscriptions, top-ups, e-tickets to events and the like are not allowed to be listed. Cryptocurrency isn't prone to charge backs or fraud, so selling aforementioned items for crypto is perfect.

3) P2P commerce across the globe. If you want to buy an item from someone within your country, you're able to do so relatively easily with the help of a bank transfer, PayPal transfer or other well-known payment method within your country. It gets trickier when you try to extend this to a global scale. A person from France can't pay a person in Bangladesh because PayPal doesn't support the latter, bank transfer fees are way too high and other methods of payment aren't supported either. Cryptocurrency comes in really handy here because anyone can start accepting it immediately without requiring any permission and not subjected to any restrictions.