Most building codes require stairways
to have at least one gripable handrail, but there are some exceptions.
Gripable handrails are required to be a specific size and distance from
the stair treads nosing.
The gripable handrail provides people with something to hold on to, while using the stairs. I could only imagine, how many potential accidents have been avoided, simply by having something to hold onto, while walking up and down a stairway.