As I understand it, originally SpaceX was planning on using propulsive landing with side-mounted thrusters and legs coming through the heatshield (i.e. what was planned for Dragon 2) on Mars, so they were developing the technology with that end in mind.

Once they decided to go straight to Starship/BFR with the movable 'wings' and raptor engines on the bottom and cancelled the dragon missions to Mars, there was less reason to go though the huge amount of work to finish developing and qualifying dragon-style propulsive landing. NASA was never super happy with it and Dragon was designed to do water landings with parachutes in case the thrusters failed anyway, so it wouldn't have been too much work to make that the only option.

This has lead to a strange situation where it seems Boeing's Starliner has ended up being more reusable than Dragon as it comes back onto land... But if they get Starship going, all this will be irrelevant.