Ooh, this is a great question as I have no hobbies and few interests. Does reading count? I would say what elevates an interest to a hobby is that you engage regularly in a hobby, are interested in improving the execution of it, and constantly consider monetizing it.
I think a hobby includes some sort of action. But I wonder where watching sports falls on the hobby/interest spectrum. I certainly spend a lot of time watching, reading, and talking about baseball. But it's mostly consuming. Me yelling at the tv doesn't necessarily constitute an action.