There are a lot of reasons for it, you surely had a rifle in your hands once and shot it.

1)Shooting always looks easy in games or movies but it's actually really tricky. I remember when we had to aim at targets around 200m-300m and my whole squad (equipped with scoped G36) had a really hard time actually hitting the targets.

Now imagine a semi-trained dude shooting an iron sighted, un-zeroed ak at something, he won't hit shit and he knows that.

2) When you're in combat you really do fear getting hit. Most of the guys hipfiring hear (also hip fired) bullets whizzing past them so hold their guns above their cover and blindly shoot in the direction, it gives you a feel of "yeah even if i have no control of the situation whatsoever i try to do something against it".

That's how you get the footage of hour long clashes where both sides fire from their covers with no intention to move forward (which is the crucial part of combat, either move forward or backwards, never stay in position)

3) To your point 1): What should they aim at ? They don't know it either. Remember that in combat you rarely see your enemy at all. So you start shooting at positions you think the enemy is shooting from.

Let's say you have a 4-story building like in the SAA vs. rebels videos. You know the rebels are shooting from somewhere in the building, so you want to suppress that fire. What difference does it now make if you aim at the first, second, third and forth floor to place accurate shots if you can just unload half of your magazine into the whole building because, you know, some bullets will land on the floors either.

4) To your point 3): Exactly this. the lack of training, disciplined soldiers and guerrilla tactics leads to either stalemate or back and forth moving front lines.

Imagine tactics like this: The SAA got Intel from locals that rebels have been seen in that part of the town. So the SAA groups up, starts shelling the area and starts moving in heavy armor which starts shooting at every building, a lone rebel runs to some window, quickly unloads his RPG on the tank an thus destroying it. SAA falls back, tries the same ambush on the next days with even more shelling etc. Finally nothing much of buildings are left, rebels withdraw, SAA celebrate their success until rebels move back there again in 5 months. That's how you see the utterly completely destroyed neighborhoods ...