I water my lawn once or twice a week when it's dry. Nothing crazy, just a misting for 10-15 mins. I don't think it's wasting water to help an ecosystem blossom. The vast majority of grass seed we see in the UK would be native grasses. Mine is mixed hardy horse paddock grass. Grows like wildfire, and the bugs love it.
I still think even monoculture grass lawn is a good middle ground between nothing living at all and a wildflower meadow or the like. Not everyone cares about the plants around them, but grass and soil beats concrete or bare earth.