What is the theoretical justification for state averaging in SA-CASSCF?

According to the molpro manual, section 7.3:



> 
> In order to compute excited states it is usually best to optimize the
>  energy average for all states under consideration. This avoids
>  root-flipping problems during the optimization process and yields a
>  single set of compromise orbitals for all states.
> 
> 
> 


Is see that SA-CASSCF is quite standard in the literature, even in cases when root-flipping wouldn't necessarily cause an issue, and I don't understand why making such compromise to obtain a single set of orbitals makes theoretical sense. Isn't it better to find the set of orbitals and the CI vector that minimizes the energy for each of the roots of interest? 


