Why do I have to press "claim rewards" in order to receive my rewards?

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• When I add tokens to stake or when I unstake, my claimable rewards becomes 0.
• I'm not receiving any staking rewards.
• Why does it take time to unstake my token?
• What is the difference between tokens that have an "unstake" function and tokens that do not?
• I cannot see "Claim Reward" button on staking page.