I like how you use the law as a reason despite the law already restricting how you can pay.
The U.S. used to have coinage limits as well, but tied to dollar amounts rather than total coins, but those were stricken to make all coinage legal tender.
Which is even funnier when you think about it. Because originally coinage was the tender. It was stamped and minted precious metals of a certain weight.
Bills were basically receipts or scrip that represented those metals. Essentially a token saying "Dude, it's cool, I do really have this money somewhere". And now the big hubaloo is the switch to electronic payments and people are freaking out because it's not real because it's not paper, which also isn't real. Just a representation of credit you have that's backed by the government that issued the bill.
And I wouldn't say it's a need, it's more of a convenience. Instead of mucking about with bills and coins, counting out change, etc, I just swipe or insert. No need to keep anything organized, etc. No need to pop off and find an ATM every week. And I'm not saying it's an earth-shattering difference. It's more like the convenience of going out to eat rather than cooking for the night. But in this case, I'm doing it almost every night.
And I kind of went through the same phases you're describing. When debit cards were becoming ubiquitous, you'd use them for the "big" things. Going out to a "proper" restaurant, stuff that cost more than the cash in your wallet, etc. And yeah, it was like "Ugh, I'm buying a soda with my card, awkward. Sorry". When the first fast food places installed card readers it was like "This is weird. Buying a Big Mac with a card."
But now, the situation is nearly flipped. It's more like when I go through the drive through, if we have to do the cash passing game, I feel bad. The card is simple. Hand one thing over, get it back with a slip of paper.