Thats because Reya Dawnbringer, in addition to a not too shabby 4/6 Power and Toughness (though you may be expecting more for such an expensive card), can bring one creature per turn back from your graveyard, returning it straight to your battlefield
Although this artifact isn't too powerful on its own, the PuPu UFO is incredibly easy to incorporate into your deck as a colorless artifact
In fact, while you get to look at three, after casting it you have the same number of cards in your hand as before
Fast forward to now
Red is meant to be a proactive color, but the problem is that making waves is heavily discouraged in a format with three opponents
Whenever any other nontoken Creature enters the battlefield under your control, you get to investigate, which means you create a Clue token