Because they spend so long in captivity thst they become reliant on people. Keiko is the only somewhat successful story but even then he only lived about 5 years and at 27 years old died. That is the only remotely sucessful release to date and even then it wasn't that great.
Point is lolita gets her fish thrown into her mouth with probably meds to mitigate her health issues. So you see the problem with moving to open ocean is we aren't her veterinarian we don't know her medications nor has she hunted in the timd she's been in that tank since 1970. Her blindness would also prove difficult to work with as she cannot see well and has no survival skill to speak of.
So you see that were you to release a captive orca taken from the wild they won't know howto survive Keiko was kind of a not so successful story as he never adapted to life in wildfully and died because of it.
Keikos release was considered a failure. A lot of people assume it was successful it was not he died just a year after his release in 2003. He's also a prime example of how difficult it is totry and train an orca for wild living.
The fact that people claim it was a success baffles me it was a complete failure because he never adapted and died a year after his release spent most of his time in seapen and died in 2003 he was released officially in 2002. so he didn't live but a year when he was officialky released. He spent 5 years learning and he still didn't fully adapt.
For Keikos release to be considered a success he would have had tohave completely adapted to living in the wild which he didn't.