Ask HN: Why aren't short-term home swaps more popular?

Now that Airbnb is so big, it's practically proven that people are ok with strangers using their homes. That begs the question, why don't people do swaps? Especially now that so many people work from home.

Is it just that there isn't a great service that enables this?

(and I get that some people do swap homes, just wondering why this cheap Airbnb alternative is under utilized?)