Who works every day with assemblers, debuggers, sniffer, reverse engineering and malware research, do you think they use an antivirus?
They find 0-day exploit by analyzing thousands of code lines and they find and analyse vulnerability ... they, not the antivirus.
For the average user, antivirus, firewall, antimalware etc, with all their limitations, of course are useful tools to prevent permanent infection.
This is all very true. There are a multitude of methods for analyzing executables, libraries or any other compiled file object there is right - even most of the more hardened ones, such as those with obfuscated or even encrypted code. And employing these methods one can learn a lot about how a certain malicious piece of software functions, and based on these findings, one can develop other methods and software which specialize in preventing/stopping or controlling these malicious functions so that they may not cause harm to the file system.
However, what happens when for some wild reason, when a number of conditions are met, a malicious executable is executed, or an exploit is run through a vulnerable browser? No matter the users' proficiency in IT and computer knowledge in general, they will not be able to stop that potential intrusion without having some sort of tool running, or without having a tool to help them stop that intrusion manually. As such, a security tool (not necessarily a traditional signature-based antivirus), such as a HIPS system which alerts the user and the user is prompted to allow/deny any malicious action(s) from being performed, would be really useful.
Whether a computer user is a programmer/coder or not, regardless of their level of proficiency in IT and whether they know how to reverse engineer compiled executables/libraries or not, tools are tools, and they will always be necessary, sometimes to a greater extent, and sometimes to a lesser extent.
It would be wiser not to be so absolute as saying "no security software is required at all" or "let's bloat our system by installing all security software we can", and choose a more middle solution, such as having only a few, but powerful and versatile security tools, combined with awareness, a reasonable level of proficiency in IT, and safe computing habits.