I've considered QF to be revenue based for decades when it comes to status - in the broadest sense of SC's (and before them Tier Points) equating more or less to fare paid - at least fare class paid. When QF stopped mileage based points earn under S&F that was the other side of the coin again broadly matching the revenue equation.
Yes, UA/AA/DL are further along in terms of revenue based - at least that there are multiple ways to status earn plus mileage earn is affected by fare multipliers(plus status of course).
I think the real reason they have not all gone to a NZ airpoints type revenue system or an even tighter revenue based one is that the legacy airlines exist not in a bubble (like, for example, Southwest more or less does) where they control all the channels and have easy grasp on the revenue stream, fare paid etc. With UA for example, if I buy a ticket with UA or through certain JV partners, they KNOW how much I paid, it's equated to USD and they can do all their fare rubbish there. However say I credit ANA or SQ flights to UA it's not transparent to them.. only in the broadest sense of fare buckets(as has always been the case). Same with QF. They know your QF spend direct with them, but CX? EK? AY? Nope. Plus it gets even trickier when you factor in more complex tickets such as RTW or anything involving partners where the fare paid and revenue direct to QF is pro-rata and all that.
I think this is broadly why they still stick with things like SC's and points earn determined by the fare "levels" (eg: Disc Y, Flex Y, Business etc().. it's so complicated otherwise.
An airline like Southwest or jetBlue can manage this far more easily as, bar a few examples, they operated in a far more closed revenue environment.
IMHO.