If we don't what's the point of debating it?

To satisfy the predetermined desire to debate it.

Monkeys are determined to argue, so they will argue about free-will, and wonder if they could have chosen not to argue, and then argue about that also.

Free will doesn't matter, there's a deeper level, which is, what is the meaning of all this, the universe, us, our place in it.

And yet we dance.

The point in debating is enjoying the debate, learning new things. What else is there to do?

Because our belief in it may influence our actions...

Free will is the experience of making a decision. If we define free will as the ability to make a decision independently of our current state (sensory input, memory, emotions), that's utterly asinine. Neither are you an unfeeling, unthinking slave to entropy, simply printing outputs. You are an introspective machine, which can ask itself why it made decisions and update its own internal state to make different decisions in the future. That's what "free will" is.

Debating its existence serves the same purpose regardless of its existence.