The reason current cargo providers have not been doing expedited rendezvous is because cargo can take the wait. The rapid rendezvous trajectory requires the ISS to be in a precise point in its orbit and requires exact timing on launch. It also requires precisely timed burns by the craft in orbit which leave little room for delays. All of this restricts the number and frequency of launch windows.

The reason Russia and Soyuz started doing expedited rendezvous is because the Soyuz is particularly cramped for 3 people, and getting the astronauts to the ISS faster keeps them happy and makes the adjustment to zero-g easier.

As EchoLogic has mentioned Dragon 2 will perform the fast rendezvous with crew like the Soyuz.

Update: Hans Koenigsmann, Director of Mission Assurance, said that short rendezvous profiles are possible for current Dragon 1 and future Dragon 2 missions

Source:
CRS-4 Mission Brief, Relevant part at 35:20

The reason current cargo providers have not been doing expedited rendezvous is because cargo can take the wait. The rapid rendezvous trajectory requires the ISS to be in a precise point in its orbit and requires exact timing on launch. It also requires precisely timed burns by the craft in orbit which leave little room for delays. All of this restricts the number and frequency of launch windows.

The reason Russia and Soyuz started doing expedited rendezvous is because the Soyuz is particularly cramped for 3 people, and getting the astronauts to the ISS faster keeps them happy and makes the adjustment to zero-g easier.

As EchoLogic has mentioned Dragon 2 will perform the fast rendezvous with crew like the Soyuz.

Update: Hans Koenigsmann, Director of Mission Assurance, said that short rendezvous profiles are possible for current Dragon 1 and future Dragon 2 missions

Source:
CRS-4 Mission Brief, Relevant part at 35:20

The reason current cargo providers have not been doing expedited rendezvous is because cargo can take the wait. The rapid rendezvous trajectory requires the ISS to be in a precise point in its orbit and requires exact timing on launch. It also requires precisely timed burns by the craft in orbit which leave little room for delays. All of this restricts the number and frequency of launch windows.

The reason Russia and Soyuz started doing expedited rendezvous is because the Soyuz is particularly cramped for 3 people, and getting the astronauts to the ISS faster keeps them happy and makes the adjustment to zero-g easier.

As EchoLogic has mentioned Dragon 2 will perform the fast rendezvous with crew like the Soyuz.

The reason current cargo providers have not been doing expedited rendezvous is because cargo can take the wait. The rapid rendezvous trajectory requires the ISS to be in a precise point in its orbit and requires exact timing on launch. It also requires precisely timed burns by the craft in orbit which leave little room for delays. All of this restricts the number and frequency of launch windows.

The reason Russia and Soyuz started doing expedited rendezvous is because the Soyuz is particularly cramped for 3 people, and getting the astronauts to the ISS faster keeps them happy and makes the adjustment to zero-g easier.

As EchoLogic has mentioned Dragon 2 will perform the fast rendezvous with crew like the Soyuz.

Update: Hans Koenigsmann, Director of Mission Assurance, said that short rendezvous profiles are possible for current Dragon 1 and future Dragon 2 missions

Source:
CRS-4 Mission Brief, Relevant part at 35:20