Because then you miss out on a lot of more recent content that'll become a classic in the future. Also, translations are copyrighted. There's 500 year old public domain stuff that's been translated in the past few decades and those aren't in the public domain. Older translations may be, but even going back 30 years, people would translate every foreign work in the style of the King James Bible. Translations in natural, modern speech are an oddly new thing.