People don't have lawns because they are intensely interested in farming. They do it because they want a large, flat, soft area outside their house. You can't play badminton with bushes and flowers in the way.
That works up to a certain size. Beyond that it's just an anachronistic emulation of an aristocratic manor house with wealth displayed by all the hard working servants cutting an immaculate lawn by scythe.
Almost no one thinks of that when they think of lawns. They are admired by many because they are aesthetically pleasing to many, which incidentally is why they were maintained by the aristocrats in the first place.
Who are we to impose our aesthetic sensibilities on others.
My view is that the local people seem to prefer a park with cut grass, and these volunteers are helping them out. If the people want something else, they should decide.