They'd prefer spiritualists over the alternative. Without being tethered to the spiritualist, the phantom would become an undead which is what they hate most.
I'd guess it would be along the lines of "Eh, it's just a matter of time". A spiritualist's phantom has only delayed the inevitable until they lose their bond with the spiritualist - who is generally mortal and will die.
Basically, they are just a bit stuck, but not an actual problem - Pharasma and the Psychopomps have an (near) infinite amount of time. And the cases of immortal spiritualist who could keep a phantom forever are to few and far between to warrant a response.
/Edit:
There are also the archetypes Usher of Lost Souls who "are common among the clergy of Pharasma", and Fated Guide whose phantoms are brought back by Pharasma herself "to complete some final task, make amends for a crime, or grant a sharply divided soul a second chance".
Apparently, she's fine with phantoms.