I don't understand why should I choose to pay Amazon in BTC or ETH,
when I can pay in € / $ without any fee.
Not only that, but I can get 5% cash back on purchases made with the store card. Why pay fees and miss out on 5% back... every single time you make a purchase? No thanks. Fiat and credit cards have their uses.
Plus, Amazon is just going to dump the crypto currencies. I don't think they are in a position to hold much or any of them. I imagine they would use a payment processor to liquidate the coins. In effect, people would be dumping the price by buying on Amazon. I'd rather they stay out of it until the markets are more liquid and less volatile. That'll take years, probably.