No snowflake blames itself on the avalanche. You may not use herbicide. You still now and create a monoculture. You probably water too. Add millions of you together and you have a problem.

No I don’t water it either. It rains in the UK often enough. It needs mowing and weeding and that’s it. The cut grass and weeds are used as compost.

Why would you water your lawn? Grass is almost impossible to kill (explicitly attacking it with herbicides aside). There is really no need.

Because there are lots of climates and many of them require constant watering to have a green lawn? Sprinkling systems are a huge business.

Sure. The grass certainly turns brown around here. But that is just a water conservation state for the grass. It doesn't mean it is dead. As soon as it does rain again, it will turn green again. That is not a reason to water a lawn. A brown lawn functions equally well as a green one. In fact better as you don't have the same need to cut it.

I imagine there are climates that are better for grass or certain species of grass that are very drought tolerant. However, in my experience, not watering a lawn will kill it. I have a few patches in my lawn that were killed this summer by lack of water due to a poorly designed sprinkler system.

The primary function of the lawn is decoration, though, and most people seem to prefer green grass.

Because in much of the world it dies and turns brown, which is considered unpleasant. Certainly lawns where I grew up (central California) needed it.

I despise lawns but there's a reason they're watered.

Remember that this is true for native grass to an area, and the first step to getting that perfect patch of green is to remove the native "weed" grass and replace it with some uniform species sold in every Lowes, from California to Kentucky.

Here in the SF Bay Area, we just went for about 7 months without a single rain drop, so one would absolutely need to water a species of grass that would never need watering in Kentucky.