Because the shortcut now points to the update file (as it should, probably), which doesn't have an specific image. Maybe they'll fix that in the future.
What you can do is right click the shortcut, Properties, Shortcut, Change Icon, and select another icon for desktop display (I choose the "tree").
Not sure why and how, but my desktop icon image for MCWIN10 is missing, so now it looks like any imageless file
Because the shortcut now points to the update file (as it should, probably), which doesn't have an specific image. Maybe they'll fix that in the future.
What you can do is right click the shortcut, Properties, Shortcut, Change Icon, and select another icon for desktop display (I choose the "tree").