The technology exists, but in practice I think people just don't want it. It is psychologically unappealing.
When people are going about their business, trying to get from point A to B but interrupted by insufficient fuel, they don't want anything that feels like major surgery being done to their car. There's a possibility for something to go wrong, and no matter how statistically unlikely, they're still going to think about it. People want this to be a casual interaction that stays in the background of their mind so they can focus on whatever they were already thinking about.
Also many people prefer to hold onto the thing they already own even if it is a convenient moment to think about changing. For example, if you have a cheap beater car that's worth $1000 and it needs an $1100 repair, you could buy a used $1000 beater car instead of fixing the one you have, but many people will pay to have theirs fixed. This is partly to avoid the hassle of buying but also partly because their beater is a known quantity to them. Back to the electric car battery swap, maybe your battery pack is a few years old and only retains 90% range, which isn't great, but how do you know the one you swap to won't have 80%? Maybe it will have 97%, but you just don't really know.
As a thought experiment, imagine a gas station near you offered two options for inflating your tires. You can pay $2 to use a self-serve air compressor, which will probably take you 5 or 10 minutes. Or, for free and in only 1 minute, a pit crew will come out and swap out your tires and rims for a different set, that they promise are the same make and model and are in equal or better condition. Do you take the pit crew option? I wouldn't.