The simple answer is that using a spoken English style often makes 
the Good News more accessible to a greater variety of people than a
literary style. The English language is always evolving and changing,
and every new generation of readers deserves a version of the
scriptures that is accessible, understandable, and natural-sounding to
them. If you’ve only heard or read the Bible in one of the relatively
traditional translations, it might come as a surprise that the people
who wrote the New Testament did not talk or write in old-fashioned
language. Like most of us, they wrote in the everyday language of
their own time and place.  The NT writers often say unexpected,
deeply challenging things, and one important way to let their words
strike home is to let them speak in a normal, everyday manner. So,
to be faithful to the authors of the New Testament, the best translation
should sound at least as normal when read aloud in English as their
writing did when it was read aloud in their language.

And that brings up a number of points in favor of a New Testament (or
Bible) translation that employs a “spoken” style. First of all, it was the
standard ancient practice to read books aloud, not silently and “without
moving your lips.” Books were composed with that in mind—that is, they
were made to be read aloud. Secondly, ancient books were written one
by one by hand, so they were relatively rare and valuable. A book like a
gospel wascomposed so that it could be read aloud to groups of hearers.
Nearly all of our NT, in fact, was written to be read aloud in Christian
communities, not simply to be read or studied privately by individuals.
For example, much of the NT consists of letters written to specific Christian
communities (i.e. churches), with the intention that they be read aloud to
the believers when received. Not only that, but Paul dictated most of his
letters to a person who put his words down on paper. So most of Paul’s
letters—perhaps all of them—are records of what Paul said with his voice,
not what he wrote with a pen. Finally, a number of the NT letters appear
to be made up of material from sermons. All of these are good reasons
to welcome and enjoy a translation of the NT into spoken English—not to
mention the fact that portions of the New Testament are read aloud in
churches every single week!