I don't know if it's the scrolling per se, so much as the more general psychological relationship we have with phones whose hardware and OS are designed to tantalize and distract. The majority of our prior experiences on the device will have primed our brain for something antithetical to the long-term concentrative state that's necessary for deep comprehension. By the same token of the advice for insomniacs to reserve your bed strictly for sleep, there's value in having purpose-built objects instead of just a singular omnipotent slab of glass.