Should text be bigger on mobile despite the fact that we're dealing with smaller screen real-estate?
- Easier to read while in motion
- Easier to read under difficult lighting
- Requires more scrolling
Put it into context. If you're sitting at a desk, the monitor is roughly 28 inches away vs. a mobile device that is 12 inches. Should it be larger if it's closer?
Four years ago, Smashing Mag found the most popular body font size on the web was 13px.
Now, most browsers default to 16px (1em/rem = 16px).
Other things to consider for readability.
These are basic guidelines that if you didn't loosely follow, would affect readability because user's rhythm, focus, and comprehension would be negatively affected.
Added source for 12-inch distance claim on mobile device
This article pretty much addresses the heart of your question and backs up many of my claims. Conclusion, smaller text on smaller screen because it's held closer.