It looks like the wheel is mounted on a hub, just like normal cars.

Adding to this: when you change your tire you’re not replacing your brake assembly.

You could probably get away with changing the tires, rather than replacing the entire wheel.

The more interesting question to me is what happens if you get a flat tire? Does everyone need to carry a spare uniwheel, or wait to get towed?

Most people wait to get towed these days on those rare occasions that they get a flat tyre. In over forty years of driving I've only had three flats. One I changed the wheel, the second I just drove slowly for twenty miles because the tyre was at the end of its useful life anyway, the third was on a narrow rural road on a slope so in the winter in the dark so I just waited for the car to be taken away on the back of a lorry.

A lot of cars don't have a spare wheel now, why would they start carrying one in the future?

I have yet to buy a car without one, but I suppose that'll be changing soon enough.

Back in the 1950s tires went flat often, so a spare that you knew how to put on was a must. These days tire technology is much better and so getting a flat is rare kit does happen of course, but it is not very common. Many cars will go through their entire life without using the spare even once. Since a spare takes up a lot of space and weight, it makes sense to get rid of it if it isn't needed much. Tow trucks have always existed, just call one to fix the tire when you have issues.

Most EVs don’t carry a spare tire anymore due to weight and space

I'm changing the wheels by myself, spring and fall. Changing the tires isn't an option, even for those who don't change by themselves. Around here there are "wheel hotels" where people keep their winter/summer tires, and when the first snow is on the way people are queuing up for the hotels to find their stored wheels and changing them. Hundreds of cars in a few days. Having to actually change the tires would make for a way too slow process (not to mention that my winter tire wheeld use very different wheel rims than my summer tire wheels).

As for flat tires.. the last time that happened to me was a few years ago. Not common these days. Except on some particular roads in the region.. the locals have complained for years that they get flat tires all the time. And that's an island, there are no towing services nearby.