Why are there so many translations?

Answer:

The primary reason given for doing a new translation is to update the language to match modern terminology. While language shifts, it doesn't shift so dramatically as to justify the multitude of translations which have come to the market in the last few decades.

There have been improvements to the base text from which translations are made, but most of these changes are minor and again don't explain the recent flood of translations.

Another reason is that the cost of doing a new translation is that the cost of creating a new translation is getting dramatically less. Computers make it easy to ensure a consistent translation and the Internet makes collaboration trivial. The typical translation committee doesn't even start from scratch. Instead, they take an older translation and then work through the text to update it and correct it. As a result people who feel that some of the older translations where less than perfect will try their hand at a newer translation.

But one of the big drivers of the translations is the publishing houses. The older texts are in the public domain and so they are constantly looking for unique products they can offer. One method they use is their study helps, which can be copyrighted. But even better from their point of view is to offer a whole new translation. Zondervan had a huge success with its New International Version and the other publishers are hoping to repeat it with their own translations.