While I find the libertarianism question interesting, it made me dumb. I took forever to realize it's irrelevant. What's important is: can you break the window next to you and jump out of it? If not, is the problem that you can't decide to do it? (If the problem is physical, get tools.) Sure, you have no good reason to do so. But if you did, could you?
Can you decide to sit in your chair upside down while people you know are watching?
If someone starts shooting up your school, can you decide to tackle them, or are you condemned to cower?
If you were a schoolteacher, could you decide to simply stop giving out homework?
I repeat: whether we decide as we do because we have to or not is irrelevant. What matters is the list of actions that are no physically impossible that, regardless, you cannot execute.
Testing your own agency is simple. Take a situation; any one will do to start. Brainstorm up all the things you can physically accomplish. Then try to decide to do all them; just go down the list. Exclude lasting harm, in case you can so decide. I haven't tried to decide to murder anyone, for example. I found deciding to do this exercise automatically motivated improvement and thus the exercise itself.
In an absolute, cosmic sense, we probably have free will. From another angle, complex structures have to be universal, or most everyone would be missing critical pieces, which means the fact I have perfect agency is very strong evidence that so do you. But cosmic agency is still unimportant. In practice, we need to talk feasible agency. Agency almost certainly atrophies exactly like muscles do. It is necessary to periodically do something whose sole merit is that it is hard to decide to do it. E.g. public schools are the opposite.
Just from the law of averages, most things will be outside the domain of things which are easy to decide to do, unless you have consciously worked hard at choosing your domain specifically to include all useful things, which I know nobody does.
No matter how good the arguments, no matter how extensive the wisdom, it is impossible to do better things without deciding to do them. Especially when they're new, deciding to do them will be hard.
For most, it seems it's hard enough to be impossible. Imagine being invited onto a TV news set, and halfway through the second question, simply inverting your position in the chair. It's hardly physically taxing. It isn't intellectually demanding. But can you do it? Sure, it's a useless action, but think about the actions that are equally impossible but not useless.
If we're talking oppression Olympics, this problem is far worse than any external oppression. Taking homework as an example, its material cost is in the negative. But it can't be used because teachers can't decide to use it, quite regardless of whether it's actually a good idea.