Shouldn't holidays be even more a reason to enable them?

Well, there were a few weekends in a row when Twitch drops were enabled, which was unusual, so maybe they're just skipping a few weekends in a row to compensate?

My guess is we'll see Twitch drops the weekend after the big global reveal of 2021's story arc.

While having a regular schedule of drops every other weekend would be nice, my recollection of drops over the last year or two (since the beginning of the drops) are that they're less likely to be on than to be off more likely to be off than on. The inability to predict with any real assurance, based on historical precedent, which weekends will have drops has caused me to miss out on drops many times, because by the time I realized drops were on it would often be Sunday afternoon. So it was actually kind of unusual when the "drops on" weekends started to occur every other weekend for a time.

And to be fair, it does make better sense, from both ZOS's and Twitch's viewpoints, to have drops follow more of an irregular pattern. From Twitch's viewpoint, this hopefully encourages viewers to watch Twitch streamers on a more regular basis, since watching regularly is generally the best way to know when drops are on. And from ZOS's viewpoint, an irregular schedule of drops lets them have occasional periods of consecutive "drops on" weekends during events that include multiple weekends, or during "free play" weeks, or coinciding with the release of a chapter or DLC or major update that introduces QoL or other new changes, or around the time of major gaming industry expos, etc. If people are more likely to tune in and watch Twitch streamers playing ESO at those times-- whether the viewers are already ESO players themselves or just curious to see what ESO is like-- then it makes good sense to have drops on at those times, both as a further enticement to get existing players to watch, and as a possible enticement to get people to start playing ESO since you need an ESO account to get a drop.

[Edited for clarity.]

I think that the answer to this otherwise conundrum has become clear: Twitch Drops died so that Endeavors could live.

Given how easy most Endeavors are to complete, I suppose that they didn't want players to be able to double-up on two sources of relatively easy Crown Crate proxy currencies.