Instead of having a million lawn mowers each belching out pollution, you use electric mowers and have all the filth at the power plant, where it can be cleaned and scrubbed better. And when new technology comes along to clean better or shift to a new form of energy production, you only have to upgrade one power plant instead of making a million people buy new mowers.
Somehow it never caught on. I don't know why.
To make it worse, people are directly near the exhausts of these machines which means that this is way, way more harmful than whatever a car manages to emit.
A laptop runs at 20W. A lawnmower runs at 1200W.
* https://en.wikipedia.org/wiki/Air_pollution Outdoor air pollution alone causes 2.1[4][5] to 4.21 million deaths annually.[1][6] Overall, air pollution causes the deaths of around 7 million people worldwide each year, and is the world's largest single environmental health risk.[1][7][8]
Productivity losses and degraded quality of life caused by air pollution are estimated to cost the world economy $5 trillion per year.[9][10][11] Various pollution control technologies and strategies are available to reduce air pollution.[12][13]
[1] - https://en.wikipedia.org/wiki/Combined_cycle_power_plant [2] - https://www.sae.org/news/2018/04/toyota-unveils-more-new-gas...
While objectively true and ignoring the fact of renewable energies that a sibling comment pointed out... power plants are cleaner than cars, even when one were to burn the same fuel - simply because modern power plants have enormously powerful particulate filters and other exhaust post-processing: fine-particulate removal using high voltage, "gas washing" to get rid of sulphur, afterburning to get rid of dioxines and other nasty compounds...