I'd say part of the reason is that none of the OW programs are directly comparable in the same way as the SkyTeam miles/segments comparison

BA has Tier Points and the back to zero rule, Qantas has Status Credits - both which require indepth analysis of a points table and fare classes.
BA won't earn on AA transatlantic and vice versa.
AA restrictions on access to lounges to its own OW elites.
Almost all the programs have rules which require minimum trips on the carriers metal.

So I think to pick a OW program requires much more individual analysis of flight patterns and what you want to get out of the program

That said - general rule is:
AA has best earn/ burn
QF best for getting Emerald if flying F/J