Imagine you're playing Esper Control and you look at this opening hand: Temple of Enlightenment, Temple of Deceit, Polluted Delta, Swamp, Island, Negate, Dig Through Time This is a hand that you're thrilled to keep against an opposing control deck like Abzan or Blue-Black Control
With the set focused on Indiana Jones-style ventures into long-forgotten ruins, it only makes sense for Magic to produce a new mechanic centered around new discoveries
Was it a difficult thing to implement
No, its not getting banned, because its only vaguely reminiscent of Coalition Victory (which is enjoying a great deal of discussion at the moment)
Of course, in Commander games starting at 40 life, being able to drop it onto the battlefield in the first turn is going to be a pretty massive advantage
In short, you want to balance the mana value of your spells to ensure you have effective spells to cast throughout the game