Not the person you are asking, but I do have GI issues due to the acidity with coffee. It can cause reflux, ulcers, and more for people if they are sensitive to the added acidity.

Not for me, but it is for some people. My current issue is more esophageal, my throat gets inflamed with too much acid then it feels like I have food stuck and can’t swallow it. Other people have stomach issues, ulcers, etc. but still want to enjoy coffee, so I think there’s plenty of reasons for cold brew served hot to exist.