In a format like Commander, where enemy boards can swell with tokens in the (sometimes literal) Blink of an eye, having a way to wipe the slate clean is invaluable
Thrasios could also let you draw your deck if youve got infinite mana

Adept Watershaper Adrix and Nev, Twincasters Alandra, Sky Dreamer Ambassador Laquatus Aquitect's Will Araumi of the Dead Tide Arctic Merfolk Atlantean Cavalry Atlantean Skirmisher Attuma, Atlantean Warlord Augur of Bolas Benthic Biomancer Benthic Criminologists Benthic Explorers Bioluminary Blockade Runner Brineborn Cutthroat Cache Raiders Caller of Gales Campus Composer Cascade Seer Cenote Scout Ceta Disciple Champions of the Shoal Cleric of Chill Depths Cold-Eyed Selkie Combine Guildmage Coral Commando Coral Fighters Coral Merfolk Coral Trickster Coralhelm Chronicler Coralhelm Commander Coralhelm Guide Cosi's Trickster Crackling Triton Cursecatcher Dakra Mystic Dalakos, Crafter of Wonders Darting Merfolk Daughter of the Deep Deepchannel Duelist Deepchannel Mentor Deepfathom Echo Deeproot Champion Deeproot Elite Deeproot Historian Deeproot Warrior Deeproot Wayfinder Deeptread Merrow Deepwater Hypnotist Deepway Navigator Disruptor of Currents Drowner Initiate Drowner of Secrets Eclipsed Merrow Emperor Mihail II Empress Galina Emry, Lurker of the Loch Enclave Cryptologist Enclave Elite Encumbered Reejerey Evidence Examiner Expedition Diviner Expedition Lookout Fallowsage Floodpits Drowner Forensic Researcher Forerunner of the Heralds Frostwind Invoker Furtive Courier Gaea's Skyfolk

It was restricted in June 1994, then unrestricted in October 1997
Youll draw extra cards when your expensive creatures enter the battlefield, you can reuse your mana rocks and mana dorks, and you can even untap a big creature that just attacked