>>Counter data point, worked in a company 10 years ago, our team was so close that we would vacation together overseas.

Worst thing ever, nothing is more harmful than a enemy who appears as a friend. This is even more true at workplace, as you are competing with your colleagues for promotions, bonuses, RSUs, travel opportunities etc. Whether one likes to acknowledge this are not, you are actually competing with them.

Another big issue with this sort of this is, it creates all kinds of untold social contracts which eventually nobody abides by. You wouldn't expect your friend to scheme behind your back to have you stack ranked in the bottom 10%, get your fired. Save his own job and have himself promoted. But in nearly every layoff cycle, this is exactly what happens.