Right, before I start this post, I really have to say to OP that it's ironsighting. I'm trying to put my spelling-Nazi phase behind me, but I just have to say it here.
Well, I won't say that ironsighting is always bad. There's something quite tension building about holding down the right mouse button, then having the gun fill half the screen, and your enemies fill the other like they're the only things in the world now. I also won't say that it's a good trend to follow, though, since the usual way that it works that you trade in some movement speed and peripheral vision in return for increased accuracy. This slows down the pace of every single encounter and discourages rapid movement and bullet-dodging in favour of sitting behind a box. Whilst games like that should definitely exist, not all games should be like that.
The idea behind making rapid-firing weapons inaccurate is understandable - random spraying is bad - but fixing it with enforced ironsighting feels like a really lazy solution, and there are better ways of fixing it.
The first example I'll give is Dystopia, specifically the Assault Rifle. A full clip contains 40 rounds. When you pull the trigger, the gun fires 7 rounds per second within a 1.48° cone. As you shoot, the firing rate steadily increases to 13 rounds per second after 20 shots, and the spread angle steadily increases to 9.96° after the 30th shot. If no shots are fired for 0.5 seconds, the accuracy and rate of fire are reset and the cycle starts again. This means that at medium range short controlled bursts are the only way to use the weapon, but when you're stuck in a close range fight, or need a long suppressive burst, the weapon adapts itself for that situation. It effectively de-ironsights itself when it needs to, giving a very creative solution to the perceived problem.
The second example is the Unreal Tournament series. Its most powerful weapons - the rocket launcher, the minigun, the flak cannon and the shock-combo - are difficult to use accurately. Not only that, but players move around at ridiculously high speeds, and the maps are designed to emphasise close ranged brawls rather than long range, drawn out gunfights. That means that it is impossible for you to keep your crosshairs over your enemy for any extended period of time. An weapon with a large spread will, therefore, hit more frequently in combat, because the random spread will help compensate for the fact that the crosshairs won't be over their target.
So, yeah, I see why games have iron sighting, and I understand the problem they're addressing, but there are far better ways of addressing that problem, and the fact that they're all doing it the same way is just tedious.