I don't understand the concept of sending cards to another account instead of focusing on one account in this system? Doesn't seem to be much of an advantage anymore because season rewards are built up based on full amount of rshares during the season. So whether those cards are earning rshares on account 1 vs account 2 I don't see the difference.

Perhaps it's a balancing of ECR algorithm I guess. Maybe there is a good range to play and switching cards so that account 1 can recharge ECR while another account plays with the cards is something to consider. Though i haven't a clue what that ECR range would be.