We do it quite often too on mil twin jets, even twins. (Once we have landed!)
Why.... ? reduces residual thrust so saving brake wear, possibly to save engine running time, or just to get ahead of the game or maybe because its cool!.
I think you'll find its done on other jets too but you just won't notice it compared to a prop. I don't suppose you'll ever be told about it but it would be a tad unwise not to mention it if one did it whilst airborne.
(Edited to add the bit about it being after landing - DOH!)