Who the actual fuck do you think you are fooling with such asinine comparisons? We are all women here, nearly all mothers, a significant proportion of us breastfed, some of us extensively. We know breasts. The only people who will cling on to the sports bra comparison are the people who are desperately trying to stay in denial for the horrible damage to young women which they have cheerled for years.
I'm mid-40s, I have naturally F cup breasts, I have been pregnant or breastfeeding for 7 years of my life, through my 30s my weight yo-yo'd and I was eventually overweight to the point of obesity. I've lost that weight now but all the changes to my breasts and the skin around them have taken a toll. And yet when I look at photographs of very young women, often still in their teens, who have been binding for a few years, the contrast is insane. They have irreversibly damaged the tissue of their breasts so badly that their breasts and mine are incomparable. It's actually hard to get my head around how damaged they are and the constant, low-level pain they must have been in to have broken down the breast tissue bit by bit.
I spend plenty of my life in a sports bra. I was reasonably athletic in my 20s and I'm highly athletic in my 40s. A sports bra does not damage my chest, it does not cause pain. On the contrary, it prevents pain. It supports my breasts when I'm jumping or running. I have a strong preference for not wearing a bra when I do upper body resistance training because I want my chest muscles to fully engage and to feel that engagement. But I have once made the mistake of going straight to burpees after weights. So I know exactly what my sports bra protects me from. The pain and damage it prevents. A binder and a sports bra are not comparable and trying to compare them is disgusting. My sports bra is an occasional aid that allows me to stay strong and healthy. A binder would destroy that.