I think it is contextual. There are people out there that are taking "upskirt" photos of women and in that case the victims should be protected from this.

Another issue is religion. It is my understanding that many Muslims do not participate in photography of humans due to their belief that it is idolatrous. Others do not want their picture taken for modesty reasons. So it would be invasive to take pictures of people against their will.

Yet another important issue is cultural. It is thought to be bad form to take pictures of colonised or marginalised people without their consent--especially if you belong to the coloniser group.