I always wondered about Toby eventually getting the morphing power and gaining a spot on the team, especially near the end of the series.
The other Hork-Bajir wouldn't have been ideal candidates to be trusted with it, as it was mentioned in #50 that they didn't have the mental capacity to be able to handle the transformation, or any of the foreign animal instincts. But Toby was always the exception though, and she would've been a great addition to the team, so it confused me as to why they never addressed this.
What
Phoenix said above is also right too, her duty was to her people first and foremost, but that still shouldn't have stopped the Animorphs from sharing their power with her. She could have been put on reserve like the auxiliaries if they were that worried, and the free hork-bajir were allies with them all the way anyway, so it would've been awesome if they had gone this route. I kept wishing for this to happen while the series was running