The reasons to play under 4 as a nonblue metagame concession or to thin out the number of 2-drops

Decklist: Narset Jeskai in Commander Narset, Enlightened Master | Illustration by Magali Villeneuve Commander (1) Planeswalkers (4) Narset, Parter of Veils Narset of the Ancient Way Saheeli, Sublime Artificer Teferi, Time Raveler Creature (1) Instants (16) Brainstorm Brainsurge Counterspell Cryptic Command Cyclonic Rift Flashback Force of Will Generous Gift Long-Term Plans Mystical Tutor Nexus of Fate Pact of Negation Response / Resurgence Swords to Plowshares Teferi's Protection Wear / Tear Sorceries (20) Approach of the Second Sun Beacon of Tomorrows Enter the Infinite Expropriate Farewell Idyllic Tutor Jeskai Revelation Karn's Temporal Sundering Mind's Desire Part the Waterveil Relentless Assault Seize the Day Supreme Verdict Temporal Mastery Temporal Trespass Terminus Time Stretch Time Warp Walk the Aeons Waves of Aggression Enchantments (7) Ashling's Prerogative Aqueous Form Fervor Mystic Remora Omniscience Thousand-Year Storm Whirlwind of Thought Artifacts (14) Arcane Signet Azorius Signet Boros Signet Chrome Mox Fellwar Stone Izzet Signet Lightning Greaves Planetarium of Wan Shi Tong Scroll Rack Sensei's Divining Top Sol Ring Strionic Resonator Talisman of Conviction Talisman of Creativity Lands (37) Access Tunnel Arena of Glory Arid Mesa Battlefield Forge Bloodstained Mire Crystal Vein Command Tower Cori Mountain Monastery Exotic Orchard Flooded Strand Glacial Fortress Hallowed Fountain Hanweir Battlements Hengegate Pathway Island Lindblum, Industrial Regency Marsh Flats Mistrise Village Misty Rainforest Mystic Monastery Needleverge Pathway Plains Polluted Delta Raugrin Triome Riverglide Pathway Rogue's Passage Rugged Prairie Sacred Foundry Shivan Reef Spire of Industry Steam Vents Sundown Pass Sulfur Falls Temple of Enlightenment Temple of Epiphany Tolaria West Wooded Foothills Your plan early on is to get some fast mana from one of your Signets or other mana rocks while Saheeli, Sublime Artificer helps you control the early game

(Bombs, Removal, Evasion, Aggro, Duds)
It's the headliner of the best ex Starter deck in Pokemon TCG Pocket, so definitely consider redeeming that one if you haven't spent your Deck Ticket already
It shines in low-curve, fast-paced decks that empty their hand quickly, especially alongside cheap legends like Ragavan, Nimble Pilferer
Using a Hypergeometric Calculator The Basics Lets say you need to draw a white mana source in the first three cards to have a functional opening hand, and your deck has 18 sources left in it