@Johnr Stupid slam on the Tea Party
The fight against metic has been going on since the seventies at least. Some money was spent on road signs in MPH and KMH. Huge reluctance to switch. The Union people ( absolutely not members of the Tea Party) are just as adamant against it. I was installing some equipment years ago and the Union Rigger asked me what height the feet needed to be set at. I said 50mm and he got his tools and left.
As a practical matter just think of the cost to change everything in the NASA data bases. It is just not cost effective. I am sure at some point it will have to be done but that is a long way off and it will be a huge and expensive project.