You realize estradiol is estrogen how are you taking gear and thinking taking estradiol is a good idea do you want to guarantee gyno? Of course the cattle get bigger adding estrogen do you think it gives hard Quality gains or water and bitch tits?
Like joswift said they are taking it for health. And basically only when they are experimenting with a nonestrogenic anabolic like Primo ran solo. Some just run a baseline 200mg of test mostly for estrogen when they do this, but now, for some reason, some forego any test at all and instead do actual supplemental estrogen to compensate. Maybe an interesting thing to try just to see what happens.
Though estrogen has muscle anabolic effects in itself. In fact even in Duchaine's time they experimented with an estrogenic product called Zeranol (Ralgro)(banned in sport). People also think estrogens are uniquely associated with water retention, forgetting all anabolic/androgenic steroids can cause water retention even if there is no estrogenic component. If I'm not mistaken estrogens affect fat
distribution more, interestingly if menopausal women are given estrogen they lose bodyfat.
You need some estrogen for proper GH and IGF-1 function and many other growth associated pathways.