There are a number of reasons why you might want to remove token approvals.
Unauthorized access or phishing scams
If a malicious smart contract or website is accidentally approved, it may have unlimited spending access to your tokens. Revoking the allowance of the contract on the token prevents further unauthorized transactions.
Revoke excessive or unnecessary permissions
Some dApps request unlimited token approvals (for example, DeFi platforms), meaning they can move any amount of tokens. If you no longer use the dApp, consider revoking the approval to limit exposure.
Avoid smart contract risks
If a smart contract has a vulnerability or bug, hackers can exploit it to withdraw tokens. Revoking access approval removes the risk of a potential exploitation affecting the wallet.