So awhile back Rito explained why they didn't want to rank ARAM.
"It’s because of the random element that I’m not sure it makes sense to ever offer a ranked mode of ARAM."
Yet, we currently are creating PBE ranked TFT, a mode with arguably even MORE of a random factor and less skill involved. So the question is Riot, how long is the random factor going to be an excuse not to offer a ranked ARAM.
While ARAM is random, the more skilled players and teamwork can adequately get good players over the 50% benchmark that a true random mode would seem to suggest. On top of that we are actually getting pseudo champion balancing more often. We're not asking for a Pro ARAM league just a fun way of measuring the better players.