The mechanic gives you the cards you need now, but if you dont use them, you lose them
Sticking to two colors also makes it slightly easier to establish your land base and more reliably get cards out quickly
You can even sink extra mana in to make a Shark if youd like
Nick Valentine, Private Eye Nick Valentine, Private Eyes gonna play great with Thopter producers and Skullclamp, but seems like a pretty narrow commander that wont work with much else
Second, thanks to Phyrexian Arena (and to a lesser extent, Dread Presence), we're likely to see a lot of our deck in any given game, so we'll draw into our one Josu Vess, Lich Knight or one Command the Dreadhorde eventually, and when we do there's a good chance it will close out the game
It gets +2/+2 and gains reach until end of turn