With tools like ImageOptim, and ImageAlpha, you can make PNGs INSANELY small with 0 or an imperceptible loss in quality.
For example, PNGs do insanely well when you have few numbers of colors that are repeating often. I've had had images that were 640px by 960px (pixel style art) that compressed down to sub 3kb with no quality loss. Good luck getting that with an SVG.
(Yes, there are certain types of images that PNGs are a terrible solution for, however, really, what I mean here is, right tool for the job.)