The main reason is because American Express was not a bank, like Chase or Discover. Amex used to only issue "Travel and Entertainment" cards, mainly to businesses and very rich individuals that traveled a lot. The number on your Visa, Discover, etc. card has to reference a bank number as well as an account number. The Amex card only references an account number. The 4-digit number on the front is simply their way of verifying that the card is valid, they still have the CVV number on the back.
Amex does have a banking side, with savings accounts and such. But the cards are a relic of the travel charge card days.
More info in this Quora answer.
answered Jul 1, 2020 at 15:25 9,744 1 1 gold badge 25 25 silver badges 52 52 bronze badgesTo subscribe to this RSS feed, copy and paste this URL into your RSS reader.
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