There's an adage dating back to at least the First World War that war is "months of boredom punctuated by moments of extreme terror"; most units were not in active combat most of the time. Generalising over the entire war is obviously impractical, but looking at contemporary records (for example the war diaries of British armoured units, some of which are available online, or US After Action Reports, many available at the Ike Skelton Digital Library) it's clear how unusual combat is compared to films or games. Large battle are rare, and even within large battles not all elements of formations are in action all the time. To take the 3rd County of London Yeomanry in 1944, for example, a regiment of around 70 tanks in the 4th Armoured Brigade, they spend the first half of the year moving from Italy back to the UK and preparing for the invasion of France. Landing on D+1, at the end of June they are involved in Operation Epsom, part of the effort to take Caen. In the whole operation of June 26th-30th there were thousands of casualties and over a hundred tanks knocked out on each side; 3rd CLY see little action until June 28th, claiming 10 vehicles for the loss of 7 tanks, then remained in position seeing no further enemy. The regiment was also involved in heavy fighting in Operation Jupiter in July and the closing of the Falaise Pocket in August, but those are very much the exception to the rule - most of the diary entries are movement and occasional small-scale skirmishes. Drilling down to an individual level is even more variable; as George MacDonald Fraser wrote in Quartered Safe Out Here: "... the battalion was in the thick of fighting for this vital strongpoint [Meiktila], which was vicious even by the standards of the Burma war, and won two decorations and a battle honour, but of this Nine Section saw nothing, and suffered no more than tired feet and ennui from marching around in the sun. [...] it always seemed rather unjust that while one company might be eating mangoes and bathing its feet, another should be getting all hell shot out of it, or that two sections could go in together and one wouldn't even see a Japanese solider all day, while the other lost half its strength clearing bunkers not far away. [...]

Another discovery was that the size and importance of an action is no yardstick of its personal unpleasantness. A big operation which commands headlines may be a dawdle for some of those involved, while the little forgotten patrol is a real horror. [...] Mention Meiktila to any surviving pensioner of my old section and he will sip his pint, nod reflectively, and say "Aye"; but drop the name of a little unheard-of pagoda that doesn't even get into the index of the big official history and he will let out an oath, sink the pint in one gulp, and start talking."

A game that was months of boredom punctuated by moments of extreme terror isn't a particularly appealing prospect, so games tend not to be realistic in that sense, putting large numbers of opposing units into close proximity without several days of marching around, getting lost, failing to rendezvous with supporting troops, and such.