Why don’t the Cadaver Collector, Eladrin, Skul…

Why don’t the Cadaver Collector, Eladrin, Skull Lord, Sorrowsworn, Steel Predator… have save proficiencies?

@mikemearls @JeremyECrawford @ChrisPerkinsDnD Why don’t the Cadaver Collector, Eladrin, Skull Lord, Sorrowsworn, Steel Predator, Super-Trolls, and many others have save proficiencies?