MTG players quickly found ways to exploit the mechanic by making oppressive, one-sided decks
It can also recover something big out of your graveyard (it costs a lot to do so, it will need to be something big)
Both cards are strong in the Pixie decks and Dimir Bounce strategies allowing an attrition-style gameplan that can take out opponents without a combat step
Smothering Tithe Arguably the crown jewel of whites ramp arsenal, Smothering Tithe capitalizes on the card draw greediness of many Magic players
Some power-up abilities require targets or have optional targets
Shamanic Revelation, Hunter's Insight, Disciple of Freyalise, and Garruk, Primal Hunter all fall into this category (although Garruk can potentially draw cards several times if your foe's let you)