I think it may be an issue with font rendering on different operating systems, screen sizes, resolutions, etc.. The webpage looks quite different on my phone vs. tablet vs. laptop. It's least readable on my tablet (Microsoft Surface 2) which has an insanely high dpi.
I know about the reader mode, and will use it if necessary. But this will loose me all pictures, gif/js animations, and whatnot. I prefer to just have readable websites. I know and accept that some people don't care, even if a more readable site wouldn't hurt their enjoyment the least. Still I prefer sites that work appropriately when I zoom, and that abstain from such visual hostilities.