Removing lawns seems to be de rigeur in this age of water conservation. There is some logic to this; lawns can drink up both water and time if you don't get the right species for your area. But if you do get the right species for your area, you can actually see more than one benefit to having a nice, green lawn instead of defaulting to non-grass groundcovers or tall wild grasses.
Grass lawns, as you know, are made up of many, many individual grass plants spread out over an area. All of these tiny plants have roots reaching down into the soil, and those roots help hold the soil in place during rain. In fact, a regular lawn is a highly effective erosion preventer. Given enough rain, any lawn could start to sag and move, of course, but in most cases, the grass and its roots keep a good grip on the soil. The grass also lets water filter down gently into the soil instead of just running off into a storm drain.
One area where lawns really can't be beat is in walkability. Sure, you can install a fake turf lawn that gets very hot in the sun, or you could install a decorative concrete pad that also gets very hot in the sun, but for a cool, open space that is soft to step on and that is relatively level (even on a hill, the grass itself will be about the same height, compared to a non-grass groundcover that might be drastically uneven and rough on your feet), plain turf grass is a total win. This is especially important if you have small children who like to run and who can't lift their feet up very high to step over larger groundcovers.
Speaking of cool spaces, grass lawns are much cooler temperature-wise than any other materials. Bare soil will be cooler than concrete, but the soil can still absorb a lot of heat. Rocks and concrete will be very hot as well. Grass, though, will be a lot easier to step on during summer. It can still get hot, but it will usually be cooler than other materials.
If you have a large open space and want to turn it into a big lawn, talk to a wholesaler about getting bulk grass seed. Ask the wholesaler about good drought-resistant grasses for your yard that aren't super-fast growers, too.