There are several verses included in the King James Version of the Bible that are not included in modern translations (NIV, ESV, etc.). As a Bible software company, Olive Tree does not make any decision to remove verses from any Bible. We publish Bibles as we receive them from the publisher without altering the text in any way.
Modern scholars and translators of Bibles like the NIV and ESV intentionally decided to leave out verses like Matthew 18:11. Since the KJV text was completed in the early 1600s, we have discovered manuscripts of the Bible that are older and believed to be more accurate than the handful used to translate the KJV. The verses in question are not found in the older manuscripts when compared to manuscripts written at a later date. The verses that were added later could have been marginal notes by a scribe or an explanatory addition by the copyist.
As a result, newer translations do not include these verses, but do make reference to them as footnotes. It is important to note that none of the missing verses alter any vital doctrine or theme of Scripture and tend to be of minor significance. I recommend reading through the introduction of the Bible you’re using for more information about the translators’ philosophy about issues like the missing verses.