Because then it loses it's magic. In fact, it already has. It's such an overhyped game mode that it's disappointing when it comes around anymore. Not to mention that certain champs are essentially an automatic win. Such as Shen and Maokai. It doesn't matter if it's all random, because no matter what happens, some champions are better than others in URF and there's almost nothing you can do about it. I still play it but I definitely believe it's not nearly as fun as the first 2 times it came around. People have created a meta around it so you can't do what you want to do which is what URF was all about, coming up with dumb ideas and seeing how they would work. The other night, some guy got flamed for playing AP Sivir. I may not agree that it's any good, but it's what he wanted to test out and he got yelled at the entire game for it. Like every game mode in League, the community has ruined it. URF is nothing special anymore and the only reason it generates any hype and gets played is because it doesn't come around very often.