I'm about to put handrails either side of an enclosed staircase, though
admittedly this is a special case since it's one of those "spacesaver"
stairs, with half-steps ( http://tinyurl.com/cu63mt3 ) which require extra
safety measures, especially on the way down. But even on a conventional
stairway I'd fit a rail each side if the space was available - and a
handrail doesn't need to extend all that far from the wall to be useful.

Bert