It was because of weight constraints. Spirit and Opportunity weighed 185 kg, while Curiosity and Preseverance both weighed around 1000kg. At that weight airbags

It was because of weight constraints. Spirit and Opportunity weighed 185 kg, while Curiosity and Preseverance both weighed around 1000kg. At that weight airbags large enough to cushion down the payload sufficiently would weigh too much. Just look at how large the spirit airbags were to support a rover that was only 1.5m square. https://en.m.wikipedia.org/wiki/Sky_crane_(landing_system)#/media/File%3APathfinder_Air_Bags_-_GPN-2000-000484.jpg https://en.m.wikipedia.org/wiki/Sky_crane_(landing_system)#/...