Why does normal queue still have such differences in team mmr averages?

Recently I was in a game where the average mmr difference was over 200 points. Now, yes it was an odd matchup for most of the lanes but never the less it was still pretty lopsided in skill level. There was one duo who both were bronze in rank and skill. And they were against a plat 2, a gold 5 and a few slivers. The rest of us were silvers.

While I am at it, this is not a rant post about a loss. This is more for showing the skill level differences between normal draft teams. In ranked I rarely ever find a gap of more than 20 at most, usually it is like 10 or fewer between team mmr averages. So why is normal draft 10 times more one sided than the worst ranked team mmr average difference? I know it is not meant to be as competitive but come on, 200+ is not an acceptable difference. At most it should be 100 points (and at a very unlikely occurrence) because at that amount and any greater would typically becomes such an uphill battle for the lower averaging team that it will not even be fun to play anymore.