Why don't more Protestant Christians use modern-English Bibles? Latin was largely substituted with Old English...but now that nobody speaks Old English, shouldn't it too be substituted?

If the bible is SO importanT; if it is the very word of god HIMSELF, then a good christian MUST learn Hebrew and Greek. I know cases of many people who admired an author so much they they learnt the original language, I for one took a special course just to read the likes of Shakespeare and Joyce, and learnt French to cope with Maupassant, Zola, Yourcenar and so forth.
It is curious, to say the least, how the catholic church (a staunch supporter of the latin mass and other rubbish) edits the bible as it pleases (besides the mandatory interpretations and footprints). In a recent edition they got rid of phrases "the brethren of the lord" by "the cousins of the lord", as your read: gross and arbitrary changes (I read it myself).
So, to answer your question, protestant christians, at least, wish to appear faithful to the only text they know, whereas catholics have renounced to think since the times of Constantine.

Here's a French riddle for you:
What's the difference between an escalator and a cigar?
Answer:
Escalators make you go up and cigars produce ashes.

Things get lost in translation.

I love the NIV myself.

In my experience, most of them do use modern translations. Still, some cling to the old King James version. I recently asked someone I know why she does, and she said because it was the Bible she grew up reading, and that's the Bible she knows. She likes the language, think it's beautiful, but I think the main reason is because the verses are more meaningful to her the way she has read them since childhood.

"A faction of those in the "The King-James-Only Movement" rejects the whole discipline of textual criticism and holds that the translators of the King James Version English Bible were guided by God, and that the KJV thus is to be taken as the authoritative English Bible. However, those who hold this opinion do not extend it to the KJV translation into English of the Apocryphal books, which were produced along with the rest of the Authorized Version. Modern translations differ from the KJV on numerous points, sometimes resulting from access to different early texts, largely as a result of work in the field of Textual Criticism. Upholders of the KJV-only position nevertheless hold that the Protestant canon of KJV is itself an inspired text and therefore remains authoritative. The King-James-Only Movement asserts that the KJV is the sole English translation free from error."
Source and further information:
http://en.wikipedia.org/wiki/Biblical_innerrancy

Because we can all read and understand old english and every time the bible is translated it changes a little.