They removed crystals box because it created a huge distraction in battle. No one cared about playing they only want crystals which they likely earn 10k in 2 hours.
Developers gave some reasons for removal of them →
Actually, the reason given to remove crystal boxes is correct. This distracted the players from the real game. It was a great move by Tanki Online. But on the other hand, this would be a great loss to new players who registered after this decision was taken. I am one of them. I was quite disappointed, but this doesn't affect me much because I earn most of my crystals by completing faily missions.
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