It's just an excuse to give out jewels (so that you keep playing). Truth is, they don't care at all about how many people reroll, all they care about is how many people SPEND. Rerolling and then spending on miracle tickets to complete the team (assuming you just got the 100% eidolon) is probably a huge part of how they make money. If not, they would have put measures it place to stop it long ago.