The seat belt is still doing its designated job even if your car goes into the river. It almost certainly improves the chances of you remaining conscious, so you can free yourself.

When AV encounters a serious and/or zero-day threat, it often doesn't do its designated job.

>Yes there are scenarios that an antivirus or antispyware don't prevent something bad from happening -- much in the same way that a seatbelt won't prevent you from drowning if your car plunges into a river.
>
>>When you really need them, seat belts will probably function.
>>
>>When you really need it, AV often does not. In fact, the more serious the threat, the more likely AV won't work.
>>
>>>Seatbelts are useless because they don't stop automobile accidents.
>>>
>>>>AV is virtually a worthless business. It cannot keep up with the changing malware landscape.