Well, DCYOU was far from a success; that initiative drove sales back down near pre-reboot numbers for the first time since 2011. There have been a lot of well received series from DCYOU, but glowing reviews dont pay the bills.
But it seems like this sort of re-branding is becoming the norm; Marvel's been doing it since 2012 with all their All NOW New & Different stuff, and the hype, not to mention the new #1's every 18 months, appears to be keeping sales at an inflated level. Once things begin to level out, a new re-branding event comes out and the process repeats. DC is just getting on that train.
So, to answer your riddle, because it sells.
Normally.