When we're bored, or find something boring, why is that?

An example of this came up in another conversation, where a fellow was saying that watching a farmer farm would be boring. And it made me wonder why in general we might find something boring, or be bored. I think I'm blessed in that I'm rarely bored, if I'm bored I ask myself what I might enjoy doing, and then do it. Do others find they are frequently bored, seldom bored, or in the middle?