Jailbreaking by definition introduces avenues for exploitation against what device security requires. Apple pays millions of dollars for security staff, auditing and security research.
It might actually be billions at this point, since they bake in some features into the silicon itself. That being said, Apple’s device security model is has many places where it is not aligned with what most people want. KTRR is a good example of a mitigation that has no effect in practice for preventing most exploits, and it’s just one of the instances where Apple tries to protect their software over you, the user.