We avoid irrigation systems wherever possible, depending on the site and the desire of the client. Less water means less weeds, less growth therefore less pruning and weeding are required. Mediteranean plants don't like water, so if they are over watered the longevity of the plant is threatened.
With the increasing number of tiger mosquitoes in the area, less water also discourages these rather annoying insects from reproducing in irrigated areas.
Limited use of water also means the garden is more in keeping with its natural surroundings, avoiding the clash of a bright green lawn with the more subdued tones of the landscape in which it is situated.