That makes no sense. SVG _is_ the vector equivalent of PNG. Just because it's defined in an xml namespace that can be directly embedded in html, doesn't mean it is somehow bound to it.
I can't write JavaScript inside of a PNG. I can't reference external resources inside of a PNG. I can't reference CSS classes inside of a PNG. I can't animate a PNG. A PNG is a simple, dumb, uncomplicated file with a minimal surface area for vulnerabilities.