A scientist might think that the historical/scientific value is more important that the personal rights of people who died millenia ago.
The people who dug up graves in the early 20th century just didn’t see the locals as people, though, which is also why most of those museums were in Europe, not anywhere near where the artifacts were found (if the artifacts were given to museums at all, instead of being sold to private collectors).
If you ask me personally: A pharaoh is a king, and fuck the king.
Who wants to have personal effects in their grave anyway? When I’m dead, I want to become soil as quickly and cheaply as possible.