KingsGambit said:
Further, modding goes against absolutely EVERYTHING corporations like Activision and EA stand for (and IMO is the reason why we'll never see another BioWare game with a toolset again).
It's actually less that and more to do with the work involved in supporting an end-user toolset vs. hacked together tools which is often the case for regular development. Then having to maintain some semblance of professional quality for said tools (i.e. no expletives in the code comments), and hitting the forums and offering guidance to those making use of it.
As with many moddable games, you get like <10% of the playerbase making use of it, and out of that 10%, like 90% would be crap, 10% decent and 1% outstanding. It's a lot of support work involved to cater for that 0.01% in hopes it would be another Counter-Strike.
Then of course, the whole IP infringement issue - like how someone ripped out the Star Wars: Jedi Knight/Academy content and ported it to NWN on the first release.
While I too, came from a mod background and went pro because of it, and prefer more companies support it, it's understandable why many do not.