I was asked why all modern translations “omit” Matt 18:11. “For the Son of man is come to save that which was lost” (KJV). The form of the question betrays the basic problem, that people think modern translations omit verses rather than other translations add verses.
There are probably two reasons for this assumption. One is that the verse is in the KJV. The second is that in modern translations the verse number is skipped.
The first Bible to have verse numbers was the Geneva Bible (1557). Verse numbers allowed readers to cross-reference passages (see Wikipedia). This was 54 years before the KJV; but like the KJV, the Geneva Bible was based on the Greek Received Text (TR) that has the verse.