Lawn is the carpeting for our outdoor spaces. Like pavement or decking, it makes the space in or gardens useful for more than growing other plants. Since it is designed to share its space with us, we give it more ground space than any other type of plant. For what it contributes, most of us do not mind giving lawn all the water and attention that it requires. It really seems indispensable.
Realistically though, most of us are lazy; and we really should be using less water in our gardens. Perhaps it would be more polite to say that we should more selectively prioritize the expenditure of limited resources and effort. Lawns that do not get much use are probably not worth all the work and water. There are easier ways of managing extra space than covering it with turf grass lawn.
Whether we like it or not, artificial turf is very undemanding, and requires no water. It is a bit too uniform and perfectly colored to convince those who bother to notice that it is not real turf, but it is still more convincing than old fashioned artificial turf. It is durable enough for children and dogs, as long as no one tries to dig in it. It does well where dark shade prevents real grass from growing.
The cost of artificial turf is an important consideration. It is relatively expensive for those who maintain their own lawns. However, artificial turf that last for many years is less expensive than paying gardeners to mow for just two or three years. The perfect uniformity of color and texture that might be unappealingly unnatural for horticultural purists is so worth the extra expense to perfectionists.
Installation of artificial turf in a new landscape is relatively easy, since irrigation can be installed only for adjacent plants that require it. Replacement of real lawn with artificial turf in an established landscape is much more challenging, or in rare situations, impractical. Trees and adjacent plants that are reliant on lawn irrigation will need to be watered (somewhat) where the original lawn was.
It seems silly and contrary to water conservation to water artificial turf, but it is sometimes necessary until roots of established plants adapt and migrate to other sources of water. This can take a few years for trees that are surrounded only by lawn. Irrigation need not be as frequent as it was to sustain turf grass, but should be sufficient to sustain any other plants while they figure things out.