what did you expect? they've said that the number of solo players per match will be limited.
And a solo player is not the only one who leaves a match after a knockdown. Nearly everyone is doing it. So SOLO Mode for all, is the only option to solve this leaving problem, cause it wouldn't matter.
Maybe if we all start to leave for some period of time, RESPAWN will be forced to bring the solo mode, cause teams make no sense anymore, or less and less people will play the mode, or maybe changing to DUOS.
Maybe thats the way to get it...I don't know