CM , on our SOP states also , that if no answer at 80 kt call ,then PM will say 'my controlls' and abort the take-off.
What are the reasons for the 80 kt call? From what I know those are:
speed check
separation between the 2 phases of RTo: low energy and high energy RTO
incapacitation check
There are different levels of incapacitation,and the fact that the plane is tracking the cl doesn't allways mean that the PF is 100% on the job.Answering a call check,at a specific time, increases the certitude about his awareness..
I knew pilots,very experienced ones,who sometimes flew the plane 'on autopilot' (and I don't mean the airplane A/P) , while their mind was somewhere else. An interrogation check will always reveal such an incapacitation , dangerous due to lack of wareness.