Why doesn’t the exchange integrate directly via CDSL/NSDL instead of asking the AP to close their existing demat account?

Why doesn’t the exchange integrate directly via CDSL/NSDL instead of asking the AP to close their existing demat account?

As per current protocol, the AP (Authorized Person) is required to close their demat account with the other broker before proceeding. Integration directly through CDSL/NSDL is not supported in this case.