I think if we're trying to find the pragmatic choice, human psychology may indeed depend on embracing the presumption or illusion of free will - at least when it comes to planning and executing our own individual futures.

But I think the presumption of free will is less pragmatic within other contexts.

For instance, if you murder someone, it makes no pragmatic difference to me whether you did it because of your free will, or because you have a neuro-divergent brain that makes you love killing people.

What does matter to me is whether I think you're likely to kill again, and what my options are to prevent it. And in that respect, it makes a difference whether you killed someone out of self-defense, or negligence, or revenge, or because you were coerced, or because you needed their money, or just because you like killing people.

Some of those scenarios portend lots more killing, and demand that society banish, quarantine, or kill you. Whereas other scenarios invite more nuanced options, like rehab (or nothing, if you killed in self defense). But none of these decisions benefit from a presumption of free will. All that matters is our ability to predict the future, based on the past.

But not only is free will unnecessary for our predictions, it also clouds our judgments.

Because the problem is that we tend to be more generous when evaluating our own free will, compared to when we make presumptions about other people's free will. And in that respect, free will basically acts as a vector for us to insert our biases onto people.

There's one other thing I'd like to say about free will, which is that it doesn't pass Occam's Razor.

Occam's Razor is the pragmatic way to form beliefs and mental models. You try to make your model as simple as possible, while still representing the problem space.

When we say that each person has free will, what we are really saying is that each person's will cannot be described by, or reduced to, more fundamental principles, and is thus a fundamental principle or axiom of the universe in itself.

And so when we claim that everyone has free will, we are essentially claiming that the universe has 8 billion or more (or infinite) fundamental axioms.

We can't necessarily prove that claim to be false, but it is a much messier, much more complex universe then one that doesn't suppose free will.

So if we go by Occam's Razor, it makes more pragmatic sense to posit a world without free will.