There's also a methodology component to it.

Regardless of the age of the remains, if I womble up with a metal detector, dig a hole and yoink out anything of value – that's grave robbing. If I fight for months for planning approval, record every detail of the site in obsessive detail, then refill any holes carefully when the funding has run out even though there's still more to discover – that's archaeology.

Plus archeology's not just graves!