I think that "Antivirus" arrived as a bandaid during the decades when security was taken seriously by some consumers but not by the OS/app software vendors. It started out as "inspect the system for signatures of malicious executables" and evolved to include "clever active mechanisms to avoid infection."
I think that there should be no need for the "active mechanisms to avoid infection" part and that is ultimately the responsibility of the OS/app vendors.
Unfortunately, through their inaction, OS/app vendors have allowed an industry to arrive. This industry will be reluctant to forfeit their position. Clearly if they think they're entitled to some consideration in the browser design, they will not go away without a fight.