Sometimes the best reason is to give a commander you really like some added power or spice with additional colors
The Boros Deck Source: Reddit Similarly to the Dimir Starter deck, most cards are pretty tame The Elegir un trabajo mechanic (Choose a job) is very similar to the For Mirrodin
This can work in control as well as agro as a 3 power evasion monster is a reasonable threat at any stage of the game, and for the bargain cost of one mana does not leave you vulnerable in order to get it out
Blue decks dig to it faster and have less in the way of things they might play instead
You cant, for example, sacrifice one creature to both Phyrexian Altar and Ashnod's Altar because costs for multiple abilities or spells cant be paid simultaneously
And, while planeswalkers don't actually gain the fox creature type, we do get this beauty of a Jace, the Mind Sculptor reprint