KYC bitcoin and privacy

I'm wondering how governments or law enforcing agencies can track bitcoins purchased from KYC exchanges (ex Binance) and then sent to a HD wallet (ex Ledger) using different addresses. Is it clear to me that Binance asks for KYC information but once a transaction it has been sent to a specific address how anyone can be sure that it belongs to the same physical person and have been not used to purchase any good or service, given for charity, to a friend or a random address?