Reply To: Anim Zemirot and Shabbtai Tzvi

In the yeshivish velt, A”Z is only said on Y”K night, due to it being full of Kabbalah, and ramozim, after the shir hayichud. I think that’s why it’s not said every shabbos- not to lose the erech of it. In fact, its brought down in halacha that if you normally daven somewhere that doesn’t say it on Shabbos and daven somewhere where it is said, you’re not allowed to walk out or do anything that would be mevazeh A”Z. I think this is the general idea why the yeshivishe oilam only says it on Y”K; due to its awesome holiness.