In locations that have no access to the grid (Eskom), off-grid systems are your only option or in certain remote locations, off-grid solar systems can be cheaper than extending power lines to connect to the grid.
Living off the grid and being self-sufficient feels good. For some people, this feeling is more important than the cost of the off grid system. Energy self-sufficiency is also a form of security. Power failures on the utility grid do not affect off-grid solar systems.