I guess it depends on what you need to carry with you. For example, I only carry my medical insurance card if I’m going to the doctor. It’s not an every day carry. Likewise, I only carry my HSA card when I am going to buy something that can be covered by the HSA (not that often). I have a work-issued credit card but I only carry it when I’m on a work trip (and even then I generally leave it in my wallet inside my luggage unless I know I will need it that day).

On 99% of days over the past two years, I’ve left my wallet at home and only carried my phone with only with two cards: my personal credit card and my drivers license.

At least in WA state, vehicle insurance card can be electronic. Health insurance card is electronic. That leaves an ID, one CC (in case "they" don't take Apple Pay), and a Health Saving Account card that oddly cannot be added to Apple Pay. Looking in the wallet, I guess I carry my credit union debit card, too.

The point is not to brag, but point out that two of those cards get taken out because there are electronic alternatives. Some states allow electronic driver's licenses, too. Subtract those three, and there's your "3-4" in your wallet. And a fuel card, FFS, for a fleet card that couldn't be an NFC/RFID fob like Exxon has had for a decade? Which in turn might as well be a reader on the pump for your NFC payment of choice.

Why wouldn't you leave fuel and vehicle insurance card in the car itself?

I suppose you would, and I print a copy for each vehicle and do just that. So I suppose it doesn't save anything, wallet-wise, but I keep electronic cards for each vehicle just because it's probably easier to find when it's needed than digging through that black abyss of a glove box.

Fuel card I don't carry, but I can picture parent comments having a fuel card attached to their name, but they might drive a different vehicle each work day ("fleet card" tells me it's for work, not personal).

In Sydney Australia, I have a Government app for an electronic Driver License. My public and private health insurance details are just numbers, the physical cards aren't necessary. So while I do still carry a wallet, it's only out of habit and I really should stop it.

Any cards which are specific for driving (e.g. fleet fuel, insurance, physical license as backup, etc) could live inside your car in a "driving wallet".