One wonders why this is necessary, although it doesn't bother me, I have to think that given the rest of the card to provide orientation, it seems unneeded.
On the upper left corner of the card, the number is always upside down. It could be confusing since both orientations are present on the card.
--it was mentioned that odd #-ed homeworlds are more military focused while the even #ed ones are more economy focused. Sure, you could just look at the red/blue, but (besides people who may be colored blind)... --it does help having a # for each of them to account for them... --and when setting up homeworlds (for 1 - 5)