If you believe in a tri-omni God, then necessitarianism makes a lot of sense.

Omnipotence, omniscience, and omnibenevolence (The 'tri-omni') + necessitarianism = Most parsimonious theism.

I believe in the tri-omni God, that is, God who is omnipotent, omniscient, and omnibenevolent. I also believe in necessitarianism. Here are some quick reasons why you should be a necessitarian [I dressed up arguments or good intuitions as questions] -

1. Why not necessitarianism (considering God always does best so God cannot do evil so you see that God's choices are already limited. Necessitarianism does not sound far away once we believe that God never does evil and shall never do evil and never did evil.)?

2. Is free will actually really that important considering only humans have free will, that is, ability to do otherwise and real possibility to do evil but God only seems to have limited free will because he can only do good?

3. If tri-omni God exists and necessitarianism is true, then goodness defeating evil is absolutely guaranteed. So, necessitarianism gives the strongest possible assurance or the absolute good news to all sentient beings ultimately. So, why not necessitarianism? If you are a universalist (like Christian Universalism or something like that.), necessitarianism is simply a step to simplicity or a parsimonious worldview replacing that messy free will belief and contingentarianism.

Necessitarianism gets rid of part of the justification of retributive justice, so if you are not a retributivist, then necessitarianism fits nicely. Necessitarianism allows for consequentialism with respect to justice.

Necessitarianism certainly does not allow the kind of moral responsibility that Free Will philosophers care about, but if you are a consequentialist or a utilitarian, then that is absolutely no problem. As Derk Pereboom says, you can even be a sort of virtue ethicist or deontologist and believe in objective morality but you just cannot believe in objective moral responsibility.

Come on! Join the side of Baruch Spinoza and Amy Karofsky!