Curiosity weighs 900 kg. NASA decided that it was too heavy for retrorockets (which would kick up too much dust and create holes in the ground around the rover) and so large (almost 3 meters across) that airbags would be too heavy [1].

Schiaparelli weighs 600 kg, closer to the size of the old Viking landers (576 kg), which did fine with retrorockets.

[1] https://science.nasa.gov/science-news/science-at-nasa/2012/3...