History tells us that serifs are more legible. They were used in print for a long time and they really improve reading experience for large blocks of text. Serif allows eye to flow more easily over the text.
How to use typography in UI Design
Wojciech Zieliński

Unfortunately this seems to only be tradition speaking. Not a lot of evidence to indicate that serifs are actually more legible, or that serifs encourage the “eye to flow more easily over the text.”