Simply because Christ is an inconvenient truth which condemns and vilifies the label, "Jehovah's Witnesses".
Acts 11:26 - "the disciples were by divine providence called Christians."
Matthew 10:18 - ".....for my sake, for a witness to them and the nations.
Mark 13:9 - "......before governors and kings for my sake, for a witness to them."
Acts 1:8 - "You will be witnesses of me...."
John 1:15 - "John bore witness about him..." [JESUS]
John 5:37 - "the Father who sent me has himself borne witness about me."
John 8:18 - "the Father who sent me bears witness about me."
John 15:26,27 - "..will bear witness about me; and YOU in turn, are to bear witness."
Acts 4:17,18 - ...upon the basis of this (Jesus') .... upon the basis of the name of Jesus.
Acts 10:39 - "And we are witnesses of all the things he [Jesus] did..."
Acts 10:43 - "To him [Jesus] all the prophets bear witness....."
Acts 13:31 - "who are now his (Jesus') witnesses to the people.
Acts 22:15 - "because you are to be a witness for him [Jesus] to all men......"
Acts 22:20 - "......the blood of Stephen your [Jesus'] witness was being spilled..."
Acts 23:11 - "..... a thorough witness on the things about me in Jerusalem..."
Acts 26:16 -"I [Jesus]..choose you as an attendant and a witness..respecting me"
1 Corinthians 1:6 - "even as the witness about the Christ..........."
1 Tim. 2:6 - "......what is to be witnessed to at its own particular times."
2 Timothy 1:8 - "............of the witness about our Lord.. [Christ]"
1 John 5:9 - "the witness God gives...the fact that he has borne witness concerning his Son."
Revelation 1:9 - "....for speaking about God and bearing witness to Jesus."
Revelation 3:8 - ...."and you kept my word and did not prove false to my name."
Revelation 12:17 - ".......and have the work of bearing witness to Jesus."
Revelation 17:6 - "........and with the blood of the witnesses of Jesus."
Revelation 19:10 -".....the work of witnessing to Jesus.... bearing witness to Jesus."
Revelation 20:4 - "............ for the witness they bore to Jesus."