Because Veigar can be countered with MR and Banshee's Veil.
Evelynn, as stated by Riot employees is a stealth champ that can stun. Stun. I cannot tell you how many times I've used an Oracle's only to see Eve, then she teleports to me for the stun, and I'm dead regardless. The only time I've ever gotten her was in the laneing phase while in mid because I HAD to pay for the wards that see invisible units. Before you go on about Twitch being stealth, the thing is, he doesn't stun. He does plain damage. They're 2 different types of surprise. Surprise you can recover from and be safe, I.E., Twitch. Or the surprise where you only see it when it's tearing your face off. That is by definition of Zileas, "anti-fun".