Well most international football games or most sports for that matter play the national anthems of both sides.
But always did find it weird to be doing it in a normal competition, Also when me and friend were seeing that in some American schools they salute the flag each morning before classes start. We both had only one thing on our mind, looks a bit like Hitler Jugend.
Might be wrong, but I also believe that its become so commercial at these events, that it really isn't any more about honouring the people that served in the military.