If they are interested in it, then why is it boring to them? Genuine question.

Being interested in something is not the same as being entertained by something. You can value the knowledge you gain from studying something even if, while you're studying the material, you find it challenging.

Is there? If the school system is any indication, people can spend literal years studying things they find boring without retaining them. Plus they can develop a hatred for the subject. Plus all sorts of bad intellectual habits like pretending they know the answer so they're allowed to move on.

Yeah you can have some bad outcomes studying stuff you're not interested in, but it can also be very rewarding. I can't really argue with you about this because I'm just pulling from my own personal experiences here. If you've never had the experience of studying something dry and finding it rewarding, then there's not much I can say.