As many have pointed out, the current ecology is so disrupted (from soil changes, nutrient pollution, invasives, etc) that simply stopping mowing does not result in things going back to the "wilderness" state of 1000 years ago. For example, if mowing/clearing pressure is relieved, foreign under-story plants such as multi-flora rose and honeysuckle rush into that space where they did not exist formerly. Many North American woodlands were relatively open in the past. And there is no fire pressure presently to clear out the brush. Like it or not, we are now managers of the land. Even prairie restorations use high mowing as a tool to control invasives during the first few years.
And most humans are followers. Many keep their property as "lawn" simply because that is the norm. Most people don't think too carefully about it, even if they are may be thought leaders in other areas. There is simply so much going on in the modern world, and people can only worry about so much. and with our society's current detachment from nature, I don't think it even occurs to many people to question their lawn. People just keep doing what they are doing in accordance with the herd.
See how everyone
is wearing a hat in this old image!
So when the next paradigm arrives, most will similarly follow that paradigm. It is up to thought leaders such as people on this forum to find the way forward....