If you are a MASH fan you might remember the 5 o'clock Charlie episode 1973, "Every day for the past six weeks, at 5:00 o'clock p.m. on the nose, a North Korean "washout from Kamikaze school" has let loose a bomb in the general direction of the hospital's sub-ammo dump. Very affectionately known as "Five O'Clock Charlie," the only thing he hits on the nose is the time. Every day, Radar opens book on the day's exploits and takes bets on how close (in yards) Charlie will come to the sub-ammo dump. It is an occasion for cocktails and frivolity at 4077, not unlike the Kentucky Derby... until Frank demands Henry get him a "nug" from Brigadier Gen. Clayton. Capt. Phil Cardozo, the singing dentist, gives the drunken duo a new slant on things. If there is anything that will beat Frank and his nug, it is 4 dozen sheets, 18 gallons of mercurochrome and a little thing called psychology."
If you are a guy in a trench facing the enemy every day and at random time of day with no warning, a plane or helicopter pops up and fires towards your position, it does not have to hit you or even come close to hitting you. The stand to alert comes up, you lose sleep, you lose meal times ( if they feed you) lose time for the 3 S of the day, your morale starts to suffer. On MASH it became a big joke and a betting pool, but in life this would have the same effect as a sniper firing at you once or twice a day. The sniper does not have to hit anything but has the fired upon troops wondering if the snipers' aim is going to be improved upon and if the stray bullet has their name on it.
Random rockets, artillery strikes and snipers can mess with a soldier's mind and be every effect in wasting his or her time waiting the enemy to come over the hill. Also serves as a reminder we are here and you are over there, and you could be next.