Because A. It is easier to read than the KJV. And B the other modern versions were already in plain English. The same comparison would be unnecessary.
Let’s look at an example of the ever changing NIV.
Mark 1:40- 41 we read: “And there came a leper to him, beseeching him, and kneeling down to him, and saying unto him, If thou wilt, thou canst make me clean.
And Jesus, MOVED WITH COMPASSION, put forth his hand, and touched him, and saith unto him, I will; be thou clean.”
The Ever Changing NIV
The NIV 1973, 1978 and 1984 all read: “
FILLED WITH COMPASSION, Jesus reached out his hand and touched the man. “I am willing,” he said. “Be clean!”
The 2011 NIV reads, Mark 1:41"
Jesus WAS INDIGNANT. He reached out his hand and touched the man. “I am willing,” he said. “Be clean!”
It’s almost laughable to think Jesus was indignant in Mark 1:41.