Why would they care? They're applying the Fight Club formula.
Take the number of listings, A, multiply by the small proportion of scam listings, B, multiply by the average refund we post, C. A times B times C equals X. If X ... well, who cares about X, it doesn't matter - people will still book with us anyway.
Plus they also get to kick the problem down the road. If they have to face it, they might as well do it later.
Airbnb should be held responsible via law, not via the expectation that they care about their image. As long as it’s the Airbnb website or app and they are getting a commission, shrugging off issues like this should not be legal.