Choosing to play all five colors and having all the best cards in Magic available at your fingertips, only to choose to run Dromoka, the Eternal is hilarious
Those 3 life points usually didn't matter much, but occasionally they make all the difference, especially when a deck finds itself in a position to do 14 or 17 damage all at once but can't do 20
The name of the game for these commanders is to control the board, benefit from graveyard synergies, and slowly dwindle your opponents decks

Zodiark, Umbral God | Commander | Stephen Johnson Commander (1) 1 Zodiark, Umbral God Creatures (27) 1 Abhorrent Overlord 1 Accursed Marauder 1 Ayara, First of Locthwain 1 Blight-Breath Catoblepas 1 Bontu the Glorified 1 Crypt Ghast 1 Dark Confidant 1 Erebos, Bleak-Hearted 1 Erebos, God of the Dead 1 Fleshbag Marauder 1 Fumulus, the Infestation 1 Garza's Assassin 1 God-Eternal Bontu 1 Gray Merchant of Asphodel 1 Grim Servant 1 Massacre Wurm 1 Morbid Opportunist 1 Nirkana Revenant 1 Phyrexian Obliterator 1 Plaguecrafter 1 Ravenous Chupacabra 1 Rune-Scarred Demon 1 Sidisi, Undead Vizier 1 Solemn Simulacrum 1 Tergrid, God of Fright 1 Underworld Hermit 1 Valgavoth, Terror Eater Instants (10) 1 Cabal Ritual 1 Dark Ritual 1 Darkness 1 Deadly Rollick 1 Defile 1 Drag to the Underworld 1 Entomb 1 Saw in Half 1 Tragic Slip 1 Withering Torment Sorceries (9) 1 Bubbling Muck 1 Damnation 1 Diabolic Tutor 1 Dread Return 1 Exsanguinate 1 Reanimate 1 Sanguimancy 1 Sign in Blood 1 Torment of Hailfire Enchantments (6) 1 Black Market 1 Dark Prophecy 1 Dauthi Embrace 1 Gravestorm 1 Phyrexian Arena 1 Underworld Dreams Artifacts (12) 1 Aetherflux Reservoir 1 Arcane Signet 1 Basilisk Collar 1 Bolas's Citadel 1 Eye of Vecna 1 Hand of Vecna 1 Jet Medallion 1 Maskwood Nexus 1 Nyx Lotus 1 The Book of Vile Darkness 1 The Darkness Crystal 1 Trailblazer's Boots Lands (35) 30 Swamp 1 Cabal Coffers 1 Cabal Stronghold 1 Nykthos, Shrine to Nyx 1 Rogue's Passage 1 Tyrite Sanctum If you wanted to make this list a little less sweaty, you'd start by dropping out Tergrid

Rounding things out, Id recommend Serah Farron as a great cost reducer in your Legendary-matters decks