Therere are many translations because language varies so much. The translators are trying to most accurately transmit the meaning of the originals to readers. That is really a moving target.
For instance the KJV or DRB really don’t accurately transmit the original to most people now. Oh sure, with study, one can do a pretty good job, but you take a person who isn’t schooled in things and give them one of those and they are going to get a lot of passages wrong for the simple reason that those translations are really written in an English that differs quite a bit from theirs.
For instance the meaning of “let” has greatly changed. “Let the children come to me” and so on sound very different than what is actually being said. It’s a command, not a if you would would you please permit it.
One thing that happens though is that readers really in many ways won’t let some passages be properly tranlated. So “Let there be light” is still that way in all the translations I know, if you changed it to reflect how it’s a definite command, you can expect to get ashes mailed to you by irate readers who accuse you of changing God’s Word.
Anyway, in order to know the English, you need to know the target audience. The NIV has a key word in it “International” it’s not aimed just at the US, it aimed at a wide English speaking audience. So the language isn’t what we’d call elegant. It’s aimed at a very broad audience and so needs to be rather bland. it’s really an amazing work when you consider the size and varience of the intended market.
You also see a gradual development of new translations of other words.
One of the great shifts has been the Greek word monogenes. You would recognize it from John 3:16 as the “only begotten”. There’s a problem with the only begotten, it’s an incorrect translation, one that goes back a long time.
If you take the texts of the Apostles creed, you can see in Greek teh monogenes and the correct word in Latin, unicum, which pretty well perfectly translates as unique. By the time of the Nicene Creed we see the mistake. Monogenes in the Greek is then unigenitum. Unigenitum is perfectly translated only begotten, and we see in the Vulgate for instance that pattern, mongenes in the Greek is translated unigenitum in the Latin.
As newer transltions were done, they followed the Latin, really it was thought that the root of monogenes was the mono, one and the genes the same and we see in for instance gennao, which is repeatedly properly translated as begat in the first chapter of Matthew. We see that root for instance in our English word generate where something is produced.
Unfortunately that’s the wrong root. Instead monogenes has as it root, genus, which we would see in our word for classifying creatures genera or kind.
So it doesn’t mean only begotten, it means one of a kind, unique.
And so we have seen the translations and even the Creeds move from using only begotten to what is most common now is only, which is true in many cases like Jesus being the only Son. But which confuses people because they then complain aren’t we all called sons of God, well yes we are so it would be better to see the complete translation as either one of a kind or unique. The ISV has actually used unique in John 3:16 and they have been under such great criticism for it they have seriously considered changing it back to an incorrect translation.
Another area there is a lot of dispute is on gender neutrality. That is in many places the masculine and neuter forms of a word are the same.
For instance you would see in English that chairman appears to be masculine and is indeed the maculine form of the word, but it’s also the gender neutral form of the word. So a woman could still be referred to as the chairman. Now many people seem to no longer understand that. If they see chairman, they think man and only a man. This is especially common in the NE US with people under 40 years of age.
The translator is left with a problem, English doesn’t really have at this time all the pronouns it needs to handle the situation. So they end up with work arounds to transmit that it isn’t just men in view, but that often makes some other things not quite right.
People don’t often realize that all English translations have a fair degree of gender neutrality, the KJV is about 30% I think. There are many passages in the Bible where they translated the Hebrew word for son as children. That’s correct actually. Newer translations generally go further in their use of gender neutrality because generally their readers require it.
Some do seem to go too far though, where they seem to have an agenda to remove the masculine references completely, that isnt’ correct either, the goal shouldn’t be to add to scripture but to as acurately as possible transmit what was written.
So anyway, that’s a couple of reasons just in the profession of tranlating, language changes, and is different so you get a lot of translations.
There is also worldly reasons. When a publisher produces a lot of books, it’s a rather big pain in the butt to get permission to use someone else’s translation. What’s happened is that the big publishers own a translation or two and so they are free to use it as they please, it makes things quite easy.
You can even see some translations that come right out and say such. That was one big reason for the NET for instance, and so they are very liberal in how they let people use it. They aren’t a big publisher themselves, but they were being cramped by the licenses of such translations as the NIV and the NASB.
So some translations are done to have the right to a translation.
And then there are translations done in response to other translations. The HCSB falls into that, to some extent the ESV do too. The RSV motivated the production of some translations in its’ day too.
That’s probably more than you wanted to know, so I’ll stop.