Great points and well researched, thank you. This always made me think the same. If Jude quotes from the book then why wouldn't we refer to it. It made no sense, until I too looked at it and it clicked.
This was interesting that I found from Wikipedia.
Reception[edit]
The Book of Enoch was considered as scripture in the Epistle of Barnabas (16:4)[24] and by many of the early Church Fathers, such as Athenagoras,[25] Clement of Alexandria,[26] Irenaeus[27] and Tertullian,[28] who wrote c. 200 that the Book of Enoch had been rejected by the Jews because it contained prophecies pertaining to Christ.[29] However, later Fathers denied the canonicity of the book, and some even considered the Epistle of Jude uncanonical because it refers to an "apocryphal" work.[30]