Can we have them back in a new update ?
if not can we have an explanation why D3 decided to remove them ?
No.
No.
I just had a thought (and posted in another thread) but what if they’ve entered all the inactive accounts into events as well?
I entered one of the first brackets of the Arena event in platinum and I don’t recognize a single name. And there are probably 400/500 players with a score of 0.
The thought has occurred to me too. I’m in Gold, and am currently ranked first in the area with a paltry 65 points (I haven’t been going for any bonus objectives). I think it’s been long enough that anyone who’s serious about playing this event has already had a swing at it. The top 10 go as follows:
1: 65 (me!)
2: 60
3: 49
4: 48
5: 37
6:31
7:30
8: 24 (I’ve played against this guy for at least half of my matches, lucky tinykitty has a Platinum Angel…)
9: 16
10: 13
But I really can’t complain, I’m still coming first so I’m looking forward to my myth… oh… wait. 
You may well be right because, even before I did any matches, I was ranked 25th going into the 5th recharge! That’s just crazy. I’m in first in my gold bracket but 2nd only has 56 pts. Wth?
Many in my coalition including myself are playing in brackets with just a few people. If this is actually not a bug, but a feature, I welcome it. It sure is something else, and something much better, than facing Killwind 10x. I have never before seen any of the players in my bracket, two of them are actually still a challenge, and there is a nice little struggle for the top rank, so there is even suspense.
In terms of matchmaking this is kind of a progress. Still, I sense it might also just be a bug. It seems that there actually are brackets with not more than 10 people, since one of us is in one which has ranks 9 and 10 with 0 points.
Strangely, my silver bracket was not barren. I ended 17th with 80 ribbons.