Ask HN: Is non-adjustable mobile font size a real problem?

I find myself simply passing on sites/articles where I cannot adjust the font size on mobile. Care to take a guess on the percentage of sites that users choose not to read due to non-adjustable mobile font size? I'm getting the sense that a signficant portion of ones userbase is being ignored and alienated with sites that do not have pinch-zoom functionality. If this is the case, then it's fairly low hanging competitive fruit to enable this kind of functionality.