I consider it the necessary evil. FFG is a company that wants to earn money. Selling at least a second core set is a huge boon to them.
This part is not exactly true as with that second core set comes all of the other bits that cost them money, the box, the tokens, rulebook etc. They probably don't really make that much extra money off of another core set purchase.
I have to disagree in a kindly way. They probably get more discount for ordering a bigger stock to be produced. If they had to splitt, the discounts wouldn't be as high or wouldn't apply. Sure you now could say, they just have to print out the cards, but I guess they would require a second packaging etc. Also marketing would be HELL!
Imagine the game and the complement pack at the same retailer, at the same shelf, the casual player that just buys it because STAR WARS, or A GAME OF THRONES would be immeadeatily put off to see that one of the purchases wouldn't give him all the cards. Howeve if there is only the core set to display, than he would grab it and present the newest FRANCHISE game to his beloved ones and cries out in joy if he draw his favourite franchise character.
Last but not least, if they wouldn't benefit in the sale, why bother to sell the first core set in the first place and reprinting it?
So they would probably loose out on the discounts AND the impulse purchases.