URF is an insane game-mode, obviously. Coupled with the insanity are a select few champs who largely benefit from URF, while quite a few more suffer in comparison.
So, with that said, why make it random? It creates an 'ARAM' type dynamic where more than not most games are decided in champ select, why not allow players to select and ban champions? I understand allowing champs to be banned could alienate some champs, but if that's how it is then that's how it is. To further that point, if players choose champs that aren't great in URF, they at least can blame themselves instead of thinking 'well maybe next time Riot will give me a decent champ'.