#1 'The Demon' stays undefeated
Although Finn Balor has lost several matches as merely himself, when feuds are taken to the next level, he brings out 'the Demon'. It usually means the culmination of a feud is coming and that he is likely going to win.
It happened numerous times in NXT and twice recently when he defeated Baron Corbin at SummerSlam last year and Bobby Lashley at WrestleMania this year. The fact is, when 'the Demon' is slated to appear, it means that Balor is going to win.
Even though Andrade gave Balor the toughest match of his alter-ego's career, Balor still prevailed. WWE could either use this as a device to make Balor unstoppable at some point or if they wanted to, the could replace the Undertaker's WrestleMania streak with a streak for 'the Demon' at the Show of Shows.
They both have grandiose entrances and auras that other wrestlers just don't have. There's a reason why this persona only shows up a couple of times a year, and keeping that streak going at SSD was the right move. Andrade could still win the title at a later date, but the Demon's mystique needs to be kept.