The blockchain was never designed as a payments processor - it was designed as actual base money. The difference is that a payments processor plays around with numbers until things are "agreed", and then when the dust settles, sends the net balance to a more permanent settlement system for permanent "settlement".
There can be many layers in the payments processing process. In the example I described before, when you park your cornflakes too close to the person in front in the supermarket checkout queue and they get lumped in with the other person's transaction, the till staffer simply reverses it out of one and into the other. The software in the cash till buffers all that messing around and only later moves the settled balances onto the next "stage" (which isn't even the clearing bank stage yet).
A few hours later, all the till balances are dumped and reconciled and the transactions can sit in a payment processor ledger (like, say stripe) for a week where people get a chance to make claims, do chargebacks, resolve disputes and whatnot.
Maybe a week later the supermarket actually receives the money.
There are therefore several layers of "buffering" in the system - one at the cash till, another at the payment processor (Visa, Maestro etc). Only much later do the transactions actually hit the clearing banks and permanently "embed" themselves in the system.
In crypto, the blockchain is the "bottom layer" in the financial system - the permanent settlement layer. In a mature commercial economy, there's a very large gap between the payment processor and the settlement layer. i.e. you would never have a heavy duty commercial merchant doing blockchain transactions because:
a) the blockchain is not a payment processor and doesn't remotely support all the functionality needed at the point of sale
b) it's far too permanent and slow for heavy duty point of sale
On the bitcoin network, we're starting to see this "meta layer" of payment processor buffering appear. One example is the Lightning network but there are others such as coinbase that do payment buffering so that - although the bitcoin blockchain may have slow clearing times - transactions are instantaneous at the point of sale.
As the crypto economy matures, that layer will become progressively deeper and more of the front line transactional weight will be absorbed by the meta payment processing layer and possibly only a minority by the blockchain settlement layer.
Excellent points!
When the retailer swipes your card, the information is sent to a middle-man (the Acquiring Bank) which communicates with your card's issuing bank to determine if you have enough money/credit to complete the purchase. A hold for that amount is then placed on your account (if using a credit card) and decreases your available credit by that amount.
That transaction is held by the merchant until the end of the day and is bundled with all other transactions made that day and transmitted to the Acquiring Bank which begins the process of settlement. If your card was swiped and then you changed your mind and the merchant voided your purchase, the transaction will never be forwarded to the payment processor and the hold will generally drop off your account at midnight.
Credit card payments are of course reversible, unlike blockchain-based payments. In a very real sense, you could argue that settlement is not fully complete until 3-6 months after a purchase is made, because until that time limit expires, the customer could do a chargeback and the payment could be reversed (potentially allowing the equivalent of a "double spend" where you get the item and keep the money).
Also, all payments are netted and deposited in one lump sum in the merchant's account. So as a merchant, if I have 200 payments of $1 each and one refund of $50, rather than having 200 small deposits and one large debit show up in my bank account, I simply receive a payment of $150 from my payment processor. This reduces "bloat."
In the bitcoin world, services like coinbase already do this, as Tok said. If a transaction is sent from one coinbase wallet to another, the transaction actually never hits the blockchain...it's all done internally.