What connection does the 3% have to the ability to do a chargeback? The card company isn't absorbing the loss, they are just pushing it back on the merchant and collect it from them unless the merchant successfully disputes the chargeback.

I have only once in my life had to request a chargeback for some random charge I had never initiated.

Where do you live or shop that you are happy to take what is effectively a 3% pay cut for the privilege of having a slightly easier option to get your money back if someone charges you the wrong amount?

To a first approximation, the 3% isn't paying for disputes; it's paying for rewards to the customer (essentially a built-in discounting mechanism that gets to discriminate on credit rating), and for profit margin to the payment processor. Disputes are paid for by the merchant, and if you get too many of them you potentially lose the ability to process credit cards.

Credit cards in many regions outside the US can do chargebacks at 1/6th that cost or less.

The vendor pays the 3% not you (through increasingly vendors try to charge this fee to you as well). If you as the consumer had to pay 3% extra every time, do you still agree?

not every transaction is risky enough to need chargebacks. it should be unbundled.

If chargebacks were guaranteed, I might agree. But if you clickjacked with an instant checkout button, be ready for some scumbag to refuse to cancel your order, try to get you to agree to restocking fees, your card company to make you send them the same emails and complaints multiple times, and multiple phone calls...