> If so, why aren't used dealers just including a battery swap in the price?

I think that is the main thing that needs to be figured out. I suspect the problem is that you need to get OEM battery replacements for older model cars and those aren't yet readily available or cheap. We are going to need aftermarket batteries to drive price competition in the market. The current car manufacturers aren't incentivised to support a secondary market when they are still focused on primary sales. Also not in the ICE market there is much more ability to scale capacity. The supply chain constraints for EVs, and batteries are much tighter, though that keeps getting better.

Battery swaps are never going to be a thing long term, even with Nio rolling it out in areas. It adds huge amounts of weight and complexity. You have to build electrical and coolant connectors which can handle large amounts of connects and disconnects, in areas that get mucky and interact with rain, salt, snow and ice. You have to build a chassis strong enough to take an impact but also support the additional weight and space that a removable battery takes up - think of how much bigger phones with removable batteries.

I have done 900 mile road trips in EVs with 150Kw charging (low by standards of newer EVs) and charging has been a complete non problem. In fact I have more problems with plugging my car in, going to the toilet and coming back finding that I've put more power into the car than I wanted.

Batteries are lasting 200k+ miles with 85-90% original capacity in so longevity is not a problem and charging is becoming a solved problems in an increasingly large portion of the world too.