steven knew when the game would start and that the guys were coming over. why start mowing the lawn without enough time to complete it, why not just wait until after or do it the day before, or start earlier. you got to roughly know how long it takes to mow your own lawn, right?
In the 1982 supernatural horror film Poltergeist, there is a scene where Steven Freeling, played by Craig T. Nelson, is shown mowing only half of his front lawn.
The reason for this is meant to subtly foreshadow and hint at the supernatural forces that are plaguing the Freeling family and their home. By only mowing half the lawn, it creates an unsettling visual of something being "off" or not quite right in their seemingly normal suburban environment.
This subtle visual cue is one of the early signs that strange paranormal activity is afoot, before the more overt and terrifying occurrences start happening to the family. It taps into the underlying theme of the film about the dark underbelly that can fester beneath the facade of traditional American suburbia.
So while it may seem like an odd character choice at first, Steven only mowing half the lawn is an intentional device by the filmmakers to set an ominous, off-kilter tone and foreshadow the supernatural horror to come in Poltergeist.
In the Poltergeist movie, Steven only mows half the lawn because he gets distracted by a neighbor running across his yard in a panic. The script describes a scene where a neighbor named Jeff Shaw comes "running as furiously as his jelly-bowl paunch will allow" carrying a large shopping bag. He narrowly avoids colliding with the paperboy as he cuts across Steven's lawn and crashes into the front door. This interrupts Steven while he is mowing the lawn, causing him to leave half the yard unmowed when he goes to see what the commotion is about with his neighbor.