Some need to be exerted , or have an ink cost to activate
Licia costs one less generic mana for each life you gained each turn, potentially even reducing its costs down to her three colored mana
Part of a cycle that features the almost-as-broken Gaea's Cradle and somehow the hilariously unbroken Shivan Gorge, Tolarian Academy taps to make a mana for each artifact you control, which led to decks that would dump their entire hand of cheap artifacts, make a ton of mana by tapping and maybe untapping Tolarian Academy, and then use big card-draw spells like Windfall and Stroke of Genius to refill before eventually milling the opponent out with Stroke of Genius, potentially all on Turn 1
Ichor Wellspring Back in Odyssey , Magic hatched a cycle of egg artifacts like Darkwater Egg
And, as far as the rules go, there's a difference between cards that literally say draw in their text, and cards that say put a card into your hand or some similar wording
Let's pause and take a looksee at some of the best cards ever printed
