I agree that human agency is a factor in the allowance of evil, though I draw distinction in thinking that human choice is the primary reason for God allowing evil. 

The reasons for the allowance of evil on the part of a just, holy, and loving God are going to vary—sometimes it is for disciplinary purposes (like a father would discipline the son in whom he loves), sometimes it is allowing an unruly and rebellious people to have exactly what they want and be faced with the consequences (Example: We don't want to submit to the good design for sex as being between one man and one woman in marriage and instead give God the middle finger by fornicating outside of marriage and producing pornography and incentivizing adultery and inventing a spectrum of gender identities and castrating young children through surgery and puberty blockers—all of which is disastrous long-term for the stability and health of any civilization, and God simply says "you want that, sure, have at it", allowing people to simply walk headlong into the natural consequences that inevitably come as a result of their rebellion.)
Sometimes the allowance of evil is to display his glory in overcoming that evil.  And I'm sure there are many other reasons God in his wisdom has that we in our finitude cannot fathom. That is partly where faith comes in—not blind faith, mind you, but steadfast trust that God is good even when things are bad.