The answer is the same as why the Falcon 9 uses propulsive landing. Parachutes are heavy, and generally require a water landing which seriously damages the boo

The answer is the same as why the Falcon 9 uses propulsive landing. Parachutes are heavy, and generally require a water landing which seriously damages the booster (not to mention requires a recovery operation). The vast majority of the weight in these spacecraft is fuel, so when it's time for it to return to the pad it requires a comparatively small amount of fuel (as most of the weight has been burnt up). The fuel itself is also a tiny percentage of the total cost of the craft, at interplanetary scale $10k for a little extra fuel is nothing.