For me, I am usually flying UA for international not because of loyalty but because (1) R was available, (2) they had the cheapest discount business class, or (3) (a factor I see little commented on), I am concerned I might have to make a change, and with UA, I will effectively only lose the change fee and otherwise get the value of my ticket to use within a year, while with LH or another European carrier booked directly with them, changes are so restricted - same cities, have to rebook before original trip, in same class or higher - I will probably lose the whole thing.