The reason QF can and does do this is purely a function of its market monopoly and the ability to apply a "third line forcing" practice that is ably assisted by MIG. QF has an extensive domestic network and the lion's share of business and leisure customers needing to connect. There are really only two truly international gateways in Australia which means someone flying internationally with a domestic transfer gets herded into where QF wants them. Want the convenience of interlining your baggage, sure these are the carriers we will do it for and for this price.

The practice of collecting baggage upon arrival is a function of customs and airport. I must admit the Sydney process is a lot better than ATL which requires you to exit and re-enter the same terminal!