Free will as a philosophical concept has less to do with "I can do what I want" and more to do with "I have control over my actions/thoughts." This gets into all sorts of interesting corners, such as:

• if God exists and is all-knowing, can God know what you're about to do? If God does, is it really your choice, or just something God planned long ago?
• if God doesn't exist, then we're all products of everything that came before. Assuming that's the case, a sufficiently powerful computer with a sufficiently large amount of data could determine what you're about to do. If that's the case, is it really your choice, or are you just a really complex automaton where the inputs (your life experiences and current situation) exactly determine your actions?
• in either of the above cases, if you're unaware that another observer knows what you'll do, do you retain free will? Does free will disappear the moment you learn of this observer? Can knowing about the observer change your actions in an unpredictable way, or can actions always be predicted?

And so on. There are some interesting discussions there at the edges, like at what point AI gains free will. That can have very real moral implications (i.e. when does AI get personhood?), so it's not just idle chat.