Why do I keep getting paired against Plat/Diamond players in ARAM?

Last four or five games at least one or two of my enemies have been Plat or above. I'm Silver. Every time I'm against players like that my team gets stomped. Why is there no matchmaking in ARAM like there is in Ranked?

Yes, I'm aware that ARAM is a casual game-mode. But there's nothing fun about playing against people much better and more experienced than you at the game.