Probably because they would have difficulties with- (just a few)
John 6:68 Simon Peter answered him, "Lord, to whom shall we go? You have the words of eternal life.
John 10:28-30 I give them eternal life, and they shall never perish; no one will snatch them out of my hand. My Father, who has given them to me, is greater than all; no one can snatch them out of my Father’s hand. I and the Father are one.
1 John 5:13 I write these things to you who believe in the name of the Son of God, that you may know that you have eternal life.
Many scriptures regarding eternal life refer to Jesus and the wt doesn't have much use for Him, in my opinion.
Also just because they like to be different. Time is construct for man not God.