These could theoretically use emblems, but dont
While they were a bit of a joke among designers and collectors, they exploded in popularity in recent years, especially with the release of a few legendary creatures
My reasoning is that some X-spell payoffs like Zaxara, the Exemplary dont work with abilities
Silkweaver Elite: In Bant (White/Blue/Green), I can have something leave the battlefield, cast this, then have this leave the battlefield, then have something else leave the battlefield
So, when we make a card that speaks to great power bearing great responsibility, theres room to add mechanical complexity because folks understand the story the card is telling