These terms are very specific in the Bible. Short of learning the original languages, they best convey Biblical concepts and help communicate Biblical principles.
Using what you call "antiquated" terminology is beneficial to those who have, by trusting in Christ, escaped from bondage to perversions. They do not need to have vile memories brought back by the use of modern euphemisms that placate what God calls sins, iniquities and abominations.
Watered down human opinions and commentary masquerading as a "translation" or "version" serve to undermine the faith of immature and untrained believers. They also tend to promote the Satanic deception of Christians having the right to do whatever is right in their own eyes. That is why I pointed you to the passage in Jude earlier.
I have various commentaries which I have found useful to help learn the meaning of numerous passages. Yet, I would never consider substituting reading these and studying these in place of God's Word.
But while these "translators" attempt to make reading the Bible smooth and easy, they compromise the essential truths and clear message contained in scripture.
If these terms are antiquated, what words are more appropriate for instructing believers how God wants them to live?
adultery (moicheia) - sexual relations with spouse of another
Example (application): an "affair"
This can, in some cases, apply to remarriage of a divorced person.
fornication (porneia) - impermissible sexual relations
This term sometimes broadly refers to sexual intercourse between participants who are not married to each other. It is more specifically used (especially when contrasted with adultery in the same passage) to describe sexual relations that are intrinsically improper. That is, there are some types of sexual relations that cannot be sanctified by marriage (Lev. 18). Using the term "sexual immorality" does not convey this sense.
Example (application): homosexuality
uncleanness (akatharsia) - (primary use is) sexual activity that is not clean
Example (application): sexual relations with a woman who is menstruating
Using the term "impurity" does not convey the physical aspect of this term and hinders the most relevant application.
lasciviousness (aselgeia) - pursuit of sensual pleasure
As used in scripture - activities that sink to new moral lows; practicing greedy, unsatisfiable lusts; exploring out of the bounds of sexual norms (nature) due to desensitization.
Example (application): pornography
Using the term "debauchery" fails to communicate the meaning in a way that serves to make it applicable. Debauchery conveys extreme behavior, while the scriptural term applies to lesser offenses.
reveling (komos) - riotous or uproarious festivity
This is associated with drinking alcoholic beverages. The term "orgies" is far too strong. The reader might get the false impression that as long as they do not engage in sexual relations with a group of people, they are not guilty of revelry. This is false.
Example (application): night club activity
"Find me a teenager who can use concupiscence in a sentence. Very few can."
They need to learn. Give them enough credit to be able to learn new vocabulary. What would you advise if teenagers are completely illiterate?
The Bible was not given merely for light reading or entertainment value. It is meant to be studied, memorized, meditated upon, and applied.
Short of learning the original languages, they best convey Biblical concepts and help communicate Biblical principles. I have a working knowledge of Greek. Many of those words are antiquated in that they are no longer used in English, and they are attempts to translate broader Greek words.
For instance, "fornication" is a word I have yet to hear a teenager who hasn't been brought up reading a King James Version (a very tiny minority of teenagers, believe me) use that word. Say "sexual immorality," and they will be able to understand it. In the Greek, pornea encompasses that broader concept, anyway.
Similarly, "lasciviousness" is a word I have never encountered outside of the King James Version; "hedonism" would be a fair approximation.
They need to learn. Give them enough credit to be able to learn new vocabulary. What would you advise if teenagers are completely illiterate?
My point is that we should not be too attached to the antiquated King James renderings when there are equally, or more, valid renderings that are more easily understood. Frankly, I could care less if they don't know the King James' terms. Firstly, illiteracy isn't a religious issue, but rather a educational, economic, and societal one. Christianity endured 1400 years before the invention of the printing press; it does not require universal literacy. Secondly, I would argue that someone who doesn't recongize a word that passed out of usage 400 years ago is not illiterate.
The Bible was not given merely for light reading or entertainment value. It is meant to be studied, memorized, meditated upon, and applied.
True enough; however, antiquated renderings are not the Word of God. Rather, it is the meanings of the words (i.e., the thoughts they were meant to convey). Strictly speaking, the King James Version is not the Word of God; it is, rather, a fairly good approximation of what the Word of God is in Greek and Hebrew. There are other fairly good approximations out there too; we should not be overly attached to any.
My basic point is this this: words and language chage; God's laws and his teachings do not. We should not be so slavishly devoted to mere English words that we actually obscure the clear teachings of God. Anything that conveys the truth of God in language people actually use and understand is okay in my book.