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In this SpaceX promotional video, they indicate their plans to land a crewed capsule without a parachute, using landing thrusters. I know that Soyuz does this too, though in combination with a landing chute.
Why, in either case, but especially the no-chute-at-all configuration, is it desirable to replace a (apparently) hyper-reliable and inexpensive chute system with an (apparently) expensive and complex landing thruster system? What's the advantage?
Note that this answer refers to the final flight version of the Dragon V2. The first powered landings will be using parachutes before the system is validated for powered-only landing (see this article, thanks to Mark Adler for pointing this out).
Parachutes are passive devices that slow the vehicle but do not steer it (some parachutes can steer a bit, others more, but not the kind used for spacecraft entry, descent, and landing). So if you want to precisely land the vehicle at a designated target then you need an active system like what you are describing.
It could be possible to add parachutes to assist with the descent but the added mass and complexity is likely not worth it since the vehicle itself is already outfitted with a propulsion system that can be leveraged for descent and landing.
Also keep in mind that a parachute landing is not the softest, whereas a powered landing allows you to make a much cleaner touchdown.
It would seem that it was a design decision to build the system so that it reliably used a powered landing alone, that way the same vehicle could possibly be used for other missions (such as to Mars or the Moon).
If you're just looking at it as a mass trade, then yes, you will definitely get a mass savings by replacing a portion of your propellant with a bag full of nylon. Depending on your speed, the nylon can have a much higher "Isp" than the rockets.
However at the system level, there are other things to consider besides mass. First, parachutes are not "hyper-reliable". You need to consider the consequences of parachute failure, which is why you usually see three of them in a cluster on crewed vehicles. (Soyuz is an exception with one large parachute, though there is a smaller backup parachute you don't see. The single Soyuz 1 cosmonaut died on impact due to both parachutes failing.) Second, if you're doing a propulsive landing for the last bit, then you may need to get rid of the parachute and also make sure that it doesn't then interfere with the landing. Third, you wouldn't reuse these kinds of parachutes, so while they are relatively inexpensive for space systems, it does cost more to replace the parachutes than to refill the tanks, and they take a fair amount of integration time due to the care needed in making sure that the rigging will deploy as intended. Filling tanks, even with hypergols, can go pretty quick. As noted in another answer, you are more at the mercy of the winds while on a parachute, so if you are targeting a very small landing location (e.g. a pad), then you will have more correction to do once you go propulsive, and will need more altitude in which to do that. Or you could have a steerable parachute, which has its own efficiency and reliability issues, and you would still be correcting at the end with the rockets.
Even with all that, if you really need the down-mass capability, you may find yourself working to solve all those problems in order to incorporate a parachute system and reduce mass. But if you're in a happy place for mass, then you would want to avoid the complexity, cost, and reliability issues of parachutes.
E. Musk has answered this multiple times in interviews. This comes down to the economics of it. They are putting this entire system together to haul cargo, and the reusable portion is there to increase profits.
They are putting in place a reusable restartable engine in order to have the maximum duplication of function for the components onboard. Previously you had one system, the engine, responsible for going up, and another system, parachutes, responsible for coming down.
Parachutes are not capable of doing job #1. Rocket engines are capable of doing both job #1 and #2. You've just reduced the mass, the failure points, and complexity of your vehicle with a minimum of redesign.
Parachutes only slow the vehicle to a certain speed. That speed isn't slow enough to land a ten-story hollow metal tube with breakable components inside on land. And landing in water adds new complications for reuse of the motors.
One thing that hasn't been mentioned thus far - the powered landing engines also serve as the launch abort system. Without them, they'd need something like the Apollo Launch Escape System to carry the crewed spacecraft away from an exploding launch vehicle.
Good luck landing a Dragon with parachutes on the Moon, as well. :-)
Atmosphere. Parachutes don't work well with thin atmospheres, like Mars', and they don't work at all with no atmosphere like the Moon. The goal is to land on other bodies in our solar system - not just Earth - so we need precision and technology that works regardless of atmosphere so rockets are much more preferential than parachutes for this reason: universal landing technology.
