Because that's the rules of this game. What got you into dominion? (I think I've heard you're not too into it, but oh well)
There's a game store near me, and once in a while they let you come in and just try out the board games with a couple of friends. I told the person running it to just pick something I would like, because I went there kinda often, and that's what he picked.
Maybe "not into it" isn't the right description. More like, it's awesome, but I'm not for playing it every single day, getting super good at it, and finding engines. I prefer to just find some cards that would make the game fun for me, and play loosely. Some of the people I play with find all these cool engines, but when I do that I don't end up having as much fun.