Whoever draws the most cards and spends the most mana tends to win games, and these two cards give your opponent the option of choking themselves on mana or giving you a card and mana advantage
Team but found that it was a little too hard to do and the payoff wasn't equal to the difficulty
I play Rule of Law effects in most of my mono-white decks, so this card is a real boon in my creature-heavy decks
For example, Forge Anew is a gamechanger for this and all equipment decks
While Poison certainly has some detractors, the mechanic is also quite popular, as evidenced by the recent price rise of this Poison Counter generating card
And if you cast it with 6 mana, you can swing in for that much and, in turn, swing the game directly in your favor with a 3 card draw and gaining 3 life