There is a link to mental illness and there are plenty of people who underwent gender reassignment only to find it wasn't the issue. Imagine a world were is was not possible to change your gentles or appearance. You are left with Gender Dysphoria and Gender Dysmorphia. You'd have to treat the underlying condition, not change the body to match.
Many young people go through Dysphoria/Dysmorphia and come out the other end without change. I personally think these people need some protection from making life changing decisions they could regret. These are not unwanted tattoos.