Probably because the USDC is being held in a real bank account controlled by some unknown 3rd party who lives in some country without an extradition treaty.

Gives you a warm, fuzzy, secure feeling that everything is perfectly safe doesn't it?

how can USDC be held in a real bank account? doesnt make sense

No, it doesn't --- unless they redeem them for USD.

I doubt there is anything preventing Binance from doing whatever they want with the coins you place in their possession.

The backing of USDC held in real bank account. They need to move real USD to Circle bank to mint USDC.

is it relevant? or is it a red herring.