I'm sure there are many companies who would be willing to take the risk that Cojocaru might become injured and not be concerned with her perfectionism. Her "Sleeping Beauty" (one of the greatest performances I've ever seen [on a NY visit]) and "Giselle" had NYers running out of superlatives.
Carla Korbes is on the delicate side with regard to injuries, although more recently she's had the hard luck of having injured partners. It's part of the privilege of seeing some of the world's great dancers.
Well with Cojocaru when Polunin (whom they were grooming to be the next major star) suddenly left, the Royal let it be known to the presses that the preceding event was a disastrous rehearsal with Cojocaru. Tense rehearsals are part of the business, but the fact that the Royal Ballet talked about it openly was a sign to me that they blamed Cojocaru or she no longer had the support of the management.
The times I've seen Cojocaru she's been exquisite, but the last time I saw her (in Giselle) she seemed racked by injuries. She's said many times that in Kiev she sustained a bad foot injury but over-danced through the injury that never really healed and accumulated more injuries. I don't blame her if she just wants to give her body a break and choose a less demanding schedule.