Hydrazine on the Shuttle
One simple reason why there is hydrazine on the Shuttle is storability. Another is the very high reliability of hydrazine thrusters. They could've used something like kerosene/LOX for the orbital insertion/maneuvering/deorbit thrusters but that would've required storing quite a bit of LOX for long missions. You'd probably still end up using hydrazine for all of those little attitude control thrusters. Hydrazine was and is the best choice. You don't have to worry about igniters, either. Hydrazine sure is nasty but we have decades of experience in handling the stuff.