I figure you have the choice. You could choose to do otherwise, but you don't. If someone offers to give me a million dollars absolutely free, or to not do so, just because I could be predicted to take the million dollars doesn't mean I don't have the choice to reject it. I'm not being coerced to take it. It's just a very predictable decision.

The goal of the concept of free will is to explain that there is a possibility of an event to be 'caused' by a human (or another life form sufficiently able).

Without the concept of free will you would have to assume that the cause for the event is originating from something else (a calculation of sorts based on previous states of the universe is a commonly stated alternative).

Free will walks the line of being a physics-based process which is neither to easily deterministic such as stone being heated in the sun or too random such as a radioactive element emitting a radioactive decay at a random/statistical time but still localizes the cause for an event in some assemblage of atoms such as a living being.