Pitching is involved when there are multiple companies being considered for the same job, and generally is restricted to much bigger projects, such as corporate identities for large companies, or ads and so forth.
The idea is that each company prepares conceptual ideas, to show the direction they think they would take with the project, and the company then chooses who they think is best for the job.

I never heard DR getting hissy over being asked to pitch, as I know that they have pitched for jobs previously (such as Nike - who they later, quite famously, "fired" )

It was more a case of believing that the evolution of wipeout had gone as far as it could go without it falling into rehashing and losing it's freshness (a point GT proved very well)
It wasn't so much because they were asked to pitch, they didn't want to pitch because they didn't want to do the project full stop.


A tip in future about pitching though - say NO to free pitching. There are many companies out there that will ask you to free pitch, and if you want to be paid, you will miss out on that job - a kind of blackmail if you will. Really - do you really want to do a heap of work, and get paid $0 for it? The fact that some people actually accept these free pitches means that it will continue, and it takes the majority of the industry to step in and say no. I highly recommend you take this path for the good of yourself (both money wise and your integrity), and for the good of the profession.