One of the most important aspects of the electrical system is the quality and safety during electrical installations. Poor bonding created high resistance return path to the overcurrent devices. We always want a low-impedance path for ground-fault current to return to the utility supply transformer or source and facilitate overcurrent device operation during a ground-fault event.
Screw clamps and other improvised connections will not provide that permanent low impedance bonding required to open a circuit breaker. The worst method (as shown here) is to just wrap the wire around the pipe. Improper bonding is a safety issue.