Why do Christians do these things in the Name of Jesus?

How is it that Christians celebrate/observe days In The Name Of Jesus such as the Birth of Jesus(Christmas)? The Death of Jesus(Good Friday)? The Ressurrection of Jesus( Easter) yet The Father never commanded us to celebrate/observe such days? on the contrary the Days that Yahuah calls His Appointed Times, which He Commanded us in UYQARA(Leviticus) 23 amongst other Scriptures to Celebrate/Observe they don’t ?

AMUS(Amos) 5:21-23 I have hated, I have despised your festivals, and I am not pleased with your assemblies. 22Though you offer Me burnt offerings and your grain offerings, I do not accept them, nor do I look on your fattened peace offerings. 23Take away from Me the noise of your songs, for I do not hear the sound of your stringed instruments.