The problem is the form factor. They're broad, flat batteries under the floor of the car, because that's the most available space when you take out the drivetrain. If you wanted to make them swappable, you'd have to sacrifice the space under the hood or the trunk. Or the passenger space. And all that comes with their own safety concerns.

There is a company that does this in China. You lease the battery, and pay roughly the same amount as a tank of fuel to swap it, so not a cheap process, and it only works on a small number of vehicles. They're also losing money hand over fist, and aren't likely to last very long.

Also, a long trip is precisely when I need all my trunk space.

Yeah, I've thought about this too, but real use cases would be rare and maybe somewhere along highways for long trips, but you'd need a lot of stations in hard to predict locations to make it something people could use. Most of the time a simple recharge at night at the domicile would suffice. Add trying to get battery form factors standardized when companies can't even agree on a universal charger and challenges to upgrading vehicle frames and design if such a standard was ever adopted and it just seems unsustainable.