Evelynismyspyname
Because if you want a bright future for future generations then its important not to live in the past but to have the skills that will generate the economy of the future. It is almost universally recognised (government and in reflection of industry) that this means that the current generation needs to be much more scientific and technically minded than at present, and so we need to make space in the teaching schedule to make this happen.
I'm not suggesting that historical art cannot be enjoyed, just that its not a priority for society in schools. Society doesn't value much of it, it generally is subsidised by people not interested in it - and it detracts from what really is going to be important.
Modern art forms which are a thriving industry (music, animation, tv, film, design etc...) are of course immensely important and have come more so as our lives have improved. We need to be teaching these rather than focussing on the past.
It's not art/science - I would also say, there is no point spending time on historical sciences that are no longer relevant. The world is probabilistic, it should never be taught as clockwork for instance; and we don't need to understand 12th century medicine.
If you love the books, just read them - but really not very important for modern life or the modern economy to devote school time to them. Well rounded doesn't mean stuck in the past - hopefully you've noticed a lack of Latin hasn't caused society to collapse - but you can learn it yourself if you want.