This is compensating for the fact that font sizes dropped through the floor for years. I recall being told years ago that 16pt font was the desire, but actual

This is compensating for the fact that font sizes dropped through the floor for years. I recall being told years ago that 16pt font was the desire, but actually most sites were using a LOT of 12 pt (or equivalently close). I even recall reading that, actually, 16pt is not necessarily large enough for easy comprehension of the average reader. In the past decade designers/PMs have started to figure out that users don't read, so they aren't trying to wedge as much text in. Though I'm no fan of some iOS interface, I credit Apple with getting the concept of legible text into mainstream design thought. As far as Medium et al goes - I think the idea there is not so much the font size as not wanting to show you more than 2-3 paragraphs, lest you get a "wall of text" opinion and not read any of it.