Maybe I'm being influenced by all the "conspiracy nutters" on this board, but what if...
...What if the Society is planning some sort of huge "bombshell" in the next 2-4 years? This bombshell, they expect, would cause maybe 20, 30, even 50% of the JWs to leave.
It has been speculated here, and I tend to agree, that the Society would rather have 3 or 4 million fiercely loyal adherents than the current mix of 7 million or so zealots, lukewarm hangers-on, slackers, and inactive "ones".
Seeing a precipitous drop in the number of publishers in a short period of time would have a devastating effect on morale for even those most-rabid zealots. So let's solve the problem by making sure no one ever sees the actual publisher counts any more.
You could remove the publisher report a few months after, or even a few months before, this speculative bombshell, but that would appear to be cynical and manipulative. As we all know, the Society doesn't mind being cynical and manipulative, it just hates appearing to be so.
So, as a pre-emptive strike, why not remove the report a couple years in advance, even when the numbers are still inching upward? Then, when the bombshell hits, there is no numerical "proof" that anything is wrong.
Sure, on a local level, individual JWs might notice Kingdom Hall attendance dropping a lot, but those loyal JWs would rationalize (based on continuing, non-number-specific glowing reports in the WT & OKM) "oh, this is just a local phenomenon - overall, earthwide, the organization is still doing well".
Just thinking out loud here, trying to make sense of the avalanche of changes that are happening now, after decades of stasis.