I just think that they can revise a lot of their history to suit their purposes, but 1914 is the one they just can't let go.
Yep. The reason is because if they abandon 1914, they also abandon:
1. The Gentile Times ending in 1914
2. The establishment of the Millennium Kingdom in 1914
These are the two main rationales for rejecting the New Covenant at the Memorial.
If the Gentile Times are still going on and if Jesus hasn't begun ruling as King, then the New Covenant is still available to "whosoever".
The sole purpose for the existence of the WT is to get people to willingly reject this covenant "for the forgiveness of sins" (Mt. 26: 27-28).
Getting rid of 1914 would put their purpose in jeopardy. They will never abandon 1914 because they will NEVER open up the New Covenant to everyone.