Of course, it is necessary to conduct regular CEX audits, but not on a quarterly basis, because this requires a lot of work and time and requires companies specialized in financial audits or government agencies. Twice a year is enough.
I expect that the issue is not that simple and requires regulatory laws in the first place. Yes, auditing and review gives some confidence and security to users, but this does not prevent manipulation from occurring at any time, as has often happened.