The answer is not as complicated as some might think.

First off, the KJV Bible, written in 1611 AD, used the best resources that were available to them at the time and did a great job in ensuring that the Bible was accurately translated into the common English language. 

However, years since 1611, many older manuscripts have been discovered and carefully evaluated by scholars. Typically scholars consider older manuscripts to be more reliable (since they are closer in time to the original documents).

Therefore most modern Bible translations would exclude/omit verses that appear in the KJV translations but do not appear in the older manuscripts. 

However, it must be noted that most modern translations still include a reference to the missing verses as part of the footnotes. 

Secondly, the original manuscripts of the Bible were not divided into chapters and verses as we have them today. Humans have divided the text to make it easier for Christians around the world to teach, preach, write, and speak about the Bible.

Following the translation of the Geneva Bible in 1560, the 1611 edition of the King James Bible was the first major translation of the Bible, which slightly altered the chapter and verse divisions. All modern English translations now follow this same structure. 

The tricky part for scholars is deciding what to do when a verse assigned a number in the 1500s turns out not to be part of the original manuscript/text. Since we cannot merely alter all verses, the translators will leave the verse blank and continue with the original numbering. 

This strategy helps maintain consistency; for example, if John 3:15 were not in the original text, and if we would move John 3:16 up a verse, then everyone who quotes John 3:16 would not have a similar verse. 

Conclusion 

It is essential to keep in mind that none of the missing verses disrupts the essential Christian teachings. The key message of Jesus as the divine Son of God, the Triune Godhead, the virgin birth of Jesus, His death, burial, resurrection, ascension, and second coming all remain undeterred.

Whether you prefer the ESV, NIV, NASB, or other modern translations, you can still rest confident that it is a trustworthy translation. That it is “living and active” (Hebrews 4:12), “inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work” (2 Timothy 3:16-17).

Most importantly, the Bible you hold contains the true message of God’s plan for salvation for our lives.