> Does anyone really need to?

It feels like the rest of the post answers your own question. Yes, Vance and basically everyone below him know full well that the US acquiring Greenland would be utterly pointless and utterly disastrous.

But he won't let it go, and in the mean time he's doing lots of stuff with real world consequences like tariffs and incinerating alliances to try to get people to agree with his stupid idea. Can't even use it as a "negotiation chip" when its the fruits of actual completed negotiations being threatened and the US could put any military installations in Greenland they wanted if they said "please" instead of "we are going to take you over".