I have seen a lot of "I like this, so it is better" in this thread.
Example: Those advocating smartphone apps for payment over smartcards and the like, citing speed and ease of use.
I personally don't see how authorizing via the smartphone is faster than tapping a smartcard on the reader. Unless you have set up the app to just authorize any requested payment within the nearfield zone, which is a security nightmare.
With respect to the original topic, I started out many decades ago writing checks and using cash for most transactions. Credit cards existed, but were mostly used by gas stations and restaurants, at least at my end of the income distribution. I used them primarily as an interest free short term loan. Back when interest rates were in double digits that actually made sense. As Visa and Mastercard grew I used them more often, but in the first decade or so they weren't faster than checks, since the vendor had to drag out their imprint machine, impress the embossed information on the card on the multi-layer carbon receipt and then get them signed by the borrower. Credit card processing grew faster over time as the magnetic strip began to be used in POS terminals. Then slowed back down big time when the chip cards were introduced. For reasons unknown to me those took a long time to process. Finally better coms and better software speeded those up and today's "Tap" cards are faster than even cash. Particularly with younger cashiers who have little clue how to make change. Somewhere in this process my check usage dropped to paying monthly charges, particularly on the credit cards. Then switched most of those monthly charges to electronic transfers from one of the credit cards to take advantage of the cash back privileges. I (actually my wife, since she holds the checkbook) write a small number of checks a month to pay the credit card bills. We have chosen not to handle those payments electronically for two reasons. First, we still don't fully trust the system to be error free, or at least fully recoverable from errors. And perhaps more important, it forces us to look at these bills monthly. It would be very easy to ignore the balances if everything was auto-payed. And writing a check is less annoying than going through all of the security verifications required to do the transfers electronically manually. I am quite sure of this because occasionally when we are on holiday we have to do it.
Checks are now processed much differently than before. When I started they were obviously processed manually with rubber stamps from both the recipients bank and my bank on the checks which were returned after processing with the monthly statement. Later those stamps disappeared as more of the processing process was automated. My guess from looking at the returned checks was that the recipients bank still manually read the written information on the check, and that information was then printed (in magnetic ink in one of the machine readable fonts) on the back where the rubber stamps used to go. All subsequent processing automated. Still later, the banks stopped sending the processed checks back, instead sending only photographs. The photos are done by machinery. All this explanation to support my opinion that the costs of processing checks is minor, and mostly a sunk cost. Even maintenance costs should be minimal for quite a while since the declining volume of checks allows malfunction machinery to be retired rather than repaired. The checks I use were once freely supplied by the bank. That ended long ago. So that cost isn't an issue for the banks.
There has been much argument about transaction costs. Here in the US the best evidence of these costs come from gasoline retailors, who routinely advertise two prices for their products, one when paid cash and one for those using credit cards. The difference is typically between three and four percent. Some retailers do the same with similar percentage costs indicated. My banks have never charged for cashing checks payable to me. In the last few years I can do that via my smartphone, no need to visit a bank. It is common for banks to be reluctant to cash checks for non-account holders, mostly because of the fraud exposure. Sometimes that reluctance takes the form of a fee, more often just a refusal to perform the transaction. The checks that I still use cost me about three cents.
I do a minor amount of selling both locally and on line. I have looked into what it would take to accept credit card payments. Various options are available. None I found were free, and at my sales volume I never found it worthwhile to sign up. There are many direct transfer options, and I have both used them and received payments via them. None of them were free. The costs are generally higher than the cost for me to write a check. The check, envelope and stamp to mail it cost under a dollar, so it doesn't take a very large transaction to make the cost of the e-transaction higher.
There are still use cases beyond preference for check usage. In rural areas internet service is intermittent or non-existent. Having commerce shut down when the internet goes out makes no sense for the merchant or for the consumer needing a tank of gas or milk and diapers for the baby. Maybe Starlink will fix this, but it hasn't closed all the gaps yet.
I will echo others on this thread. I use checks less and less, but still find them appropriate for some cases. I would dislike losing them as an option, but the world wouldn't end for me. And I don't see why those who are all in for various e-transfer methods are in favor of removing the option. Excepting those who will profit from that elimination of course, but I doubt if many on this thread are in that class.