Originally Posted by Unregistered

You grossly overestimate how many rarity growths you'll be able to do. They also need to be added to the game character by character.

->Open Spoiler<-

There's also the end of Flash coming up in 2020. Nutaku doesn't seem likely to go through the effort of porting the game.

At the same time, when you look at what rarity growth characters get, they can eclipse a lot of what current 6* girls get when they bloom.

For those that want the most power, rarity growth is gonna cover a lot of that so they have no choice if they're meta chasing.