When I attended inpatient rehab I would say over 50% of the population was knitting or making these woven bracelets during meetings/sessions/groups etc.
I think a lot of people who are in recovery find using their hands to be a self soothing activity. I have noticed that I actually retain more information when I am using my hands in repetitive movements like weeding or painting, it almost puts me in a trance.
One can listen attentively while knitting, but certainly not while texting. I don't knit but I think someone knitting in a group actually brings a feeling of comfort.