Who cares if a driver can deliberately defeat these things? This is really to do with the expectations. Consider the safety belt, there is an expectation that

Who cares if a driver can deliberately defeat these things? This is really to do with the expectations. Consider the safety belt, there is an expectation that with the safety belt on, the driver will not go through the windscreen in case of an accident. It is not the case that the driver has defeated the seat belt feature by not using the seat belt. A reasonable person will not have the expectation of having the safety provided by seatbelt without put it on. Things are not as clear cut for assisted driving as can be seen in this thread.