The first reason there are different Bibles is simply that the Bible has to be translated at all. Its Old Testament was written in ancient Hebrew (with a few Aramaic passages), its New Testament in the everyday Greek of the first century; unless you read those languages, you meet Scripture through a translator. And translation is never a mechanical swap of one word for another, because languages do not line up that way: word order differs, idioms do not carry across ("heap burning coals on his head" means something particular in Hebrew), a single Greek or Hebrew word may have several English equivalents and no exact one, and the grammar is sometimes genuinely ambiguous. So a translator makes thousands of careful judgments on every book, and two faithful, learned scholars can render the same verse in two good, differently-worded ways. That is the honest source of most "different Bibles": not disagreement about the message, but more than one sound way to carry meaning from Hebrew and Greek into English. This is ancient, and the Bible even shows it happening: when Ezra's Levites read the Law to the returned exiles, they "read from the Book of the Law of God, explaining it and giving insight, so that the people could understand what was being read" (Nehemiah 8:8, Berean Standard Bible), reading plus explanation so people could understand, which is exactly what a translation is for; and the New Testament itself usually quotes the Old from the Greek Septuagint, a translation.
Two things to keep apart. First, a translation is also, unavoidably, a bit of interpretation, to put a verse in English you must often decide what an ambiguous phrase means (whether Isaiah 7:14 says "young woman" or "virgin"; how to untangle a long Greek sentence), and good translations flag the main alternatives in footnotes rather than hide them. Second, do not confuse different translations with the separate question of which books belong in the Bible, the reason a Catholic Bible has more books than a Protestant one is about the canon, not about translation, and is treated on its own. Here the subject is the same text, rendered into different English.