Would you not consider horses the original “ride’m lawn mowers”? As herbivores, with seemingly insatiable appetites, they are a very competent mower. They are fairly consistent in the length to which they will mow, and are skilled at getting into the tight corners that would otherwise require a whipper snipper.
However, there are some drawbacks.
First off, they leave their own fertilizer behind them. Although this is beneficial to the ground itself, it can be unsightly and eventually requires clean up and removal to another site. This does result in some wonderful material for gardens but takes management.
Secondly, lawn properties are not typically ‘designed’ for an herbivore to live off. They can be deficient in mineral requirements and contain undesirable/poisonous plants (such as Buttercups). As such, there would need to be some planning and potentially supplementation in place (salt/mineral blocks available and selective weeding).
Third, horses eat a lot! Unless grazing periods are limited, they can clear acres of land in a matter of days and then be complaining they are out of material. If they are not fenced properly, they will also wander to new areas – and perhaps your neighbours do not wish their lawn mown in quite this manner. Although in the grand scheme this is a fairly quick method of grass trimming – most residential properties want their lawn completed in a matter of minutes, not days. It is also moderately difficult to mobilize a horse to numerous properties – making the idea of employing a horse as a regular piece of lawn equipment laughable.
Historically, residences were not located so close together, and it was possible to graze your work horses at the end of the day on an open field – now, we need electric fence lines at minimum, although wood fencing is still good (if your horses is not a cribber) and wire fence with wooden posts works well too to contain them. Contemporary planning encourages us to mow numerous properties in an area in a small amount of time – making gasoline driven machines more efficient.
Finally, it has become a bit complex to keep a horse as merely a lawn ornament, although many people treat their horses to such a retirement. The average horse does have some duties typically, whether it be being ridden or more therapeutic responsibilities, and are always a well loved natural piece of equipment.