There is no actual need to make any card cr right now. It would only make the market go crazy and users complain.
At the moment all cards are quite well for daily tournaments without too overpowered cards affecting the game. On ELO mode
however overpowered cards still exist and will keep appearing, but those cards can be banned without need of cr'ing them.
Cr cards make completing the collection harder thus unecouraging people to try it, and in consequence people not spending
money on credits to get the cards. No money - no game. They won't do it easily
Thats odd, I consider CRs one of the main appeals of buying cards. With all the new cards coming out completing the availables isn't all that exciting, but getting hold of rarer cards is more interesting. The divide in prices also means that people can aim to complete the available collection, but still have another collecting goal with the CRs.
On top of that there is also the incentive to get as many cards as possible in the hope that some will go CR.
Then of course theres the loyalty factor, as in rewarding players who have stuck around for a long time, or who have collected a lot of cards.
I'm surprised neither Chloe nor Miss Chloe have gone CR yet, I've been expecting that for ages...