I disagree SM4.
Aircraft inbound from the north (and east) are held at 6000' until abeam the airport to allow for departing aircraft off 34R to make their noise abatement departure (a hard right turn - thinking the MARUB departure) and climb to 5000'.
There's no operational reason aircraft off 34L can't climb to and maintain 5000' straight ahead to 10ish miles and then turn right. Once clear of inbound traffic at 6000' - continue climb. I know 'cos I've done it. The only problem is it pi$%es off the locals in Manly, Fairlight and Mosman (and one bloke in Kiribilli) and they're the ones with the education, money and lawyers to advocate for a change in departures. (NIMBY).
There is no logical reason the Richmond Departure should be the normal SID for aircraft departing to the east that are too heavy to use 34R.
In short, it's a crock that's pedalled for the purpose of political expediency.