Reading books is good for your brain. Even just fiction [0].
But I do think people often approach this issue wrong. Especially, as demonstrated by the OP article:
> “Daniel Shore, the chair of Georgetown’s English department, told me that his students have trouble staying focused on even a sonnet,” Horowitch wrote.
It's a wrong question to ask why people can't focus on a sonnet.
The real question is: why do the students who are not interested in literature choose to major English? What societal and economical incentives drove them to do that?
I would say that fiction is incredibly more important than reading non-fiction, in general, for human development.
Reading sets up, programs and tunes the holodeck in your brain. The better the holodeck is programmed, the better and more accurate the simulation is.