[Lotus]

Think about it, women go through cyclic changes every month, it's quite necessary to balance out their hormones, granted they have ovaries and we don't. We do however have many of the same similar circumstances of estrogen receptors builds up of toxins and deregulation, why shouldn't we address these too?

Receptors get desensitized for various reasons (environmental toxins, drug/supplement saturation, free radicals, inflammation, cancer, etc) which stall's growth. The reason to cycle is to reset the receptors, by cycling it helps to provide betters results (synthesis) of hormones, proteins, fatty acid synthesis (FAS) etc.  Progesterone (Progesterone cream) resets estrogen receptors (ER)
 
Research for yourself about environmental toxins. Things are more complex though, certain drug interactions (and other things, scientifically proven) can cause interruptions in breast signaling pathways, I'll spare you listng the pathways here (there in the x-thread if you're interested) that do exist, here's one example.
  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6344829/

Cycling is important when taking supplements, failure to do so will result with tolerance, and the supplements will stop working.

Once your body makes the adjustments to get back to homeostasis is the time to cycle, (ie. in a 7 day plan, try 5 days on and 2 days off).

Tolerance occurs when the person no longer responds to the drug in the way that person initially responded. Stated another way, it takes a higher dose of the drug to achieve the same level of response achieved initially.