They would probably be more likely to stare at their phones instead of learning if they did.
I do think that having students sit at desks for hours at a time is not an effective way of teaching. Giving students different ways of learning is beneficial and more likely to motivate them. But that usually is more work and more expensive to do.
In an ideal world, every student would have an individualized, self paced learning program with a dedicated teacher. Unfortunately, that’s not the case for nearly any student.