This happens all the time. Your average Joburger needs to WIN. It is important for his sense of well being (and importance) that he gets in front of YOU. He is not concerned with actually getting to his destination faster. No, he just wants to beat you, and if you dare to try to prevent him from doing so, he will get very angry with you.
I have another story. This is not necessarily bad driving, but it is so common and I think it is so stupid. It happens all the time, so I will give an example.
I drive into my local Pick n Pay, behind another car. The car heads to the parking that is closest to the entrance. Note that the shops are now busy, so most of the parking lot is full. I head straight to the back, where I know there is always free parking. I park, because it does not take me long to find a free parking.
I walk into Pick n Pay, and as I am walking in, I see the car that was in front of me still waiting for a parking. Or still driving around looking for one that is close enough. Also note, I haven't had to walk particularly far. I'd say less than 50m.
I don't understand why people would rather wait for a parking instead of walking a little further. It's not like we walk much anyway, and you can get in and out of the shops much quicker if you just head straight to where you now there will be free parking.