Perhaps because the reality of being a developer is that its a pretty boring job most of the time. Once you have worked at a few different companies on a few varying projects with a few different technologies you realise that 90% of the time you are building CRUD applications. Also working on other people's code which is significantly worse than your own can be frustrating.

So for me having a competitive element to what i consider a fairly boring job definitely makes it much less boring. As for rudeness and arrogance I try not to be those things but if somebody else is i just ignore it. Simple as.

Developers who are not team players do not make it far in my experience.