I have 5 years command on 777s and don't know the answer - it is a common design feature of most Boeing aircraft I have flown.
As it is "designed" into the system there must have been a conscious decision to make it so and the closest I can get is that initiating a go around after touchdown is extremely rare. It is also inadvisable in some circumstances (after reverse thrust selected for instance) such that special simulator training is given to cover just such situations.
Not wishing to pre-judge the EK accident I would think the lack of TOGA after landing might feature in the report - meet here in two years?