Dirty Hipsters said:
I call bullshit on the idea of developers using an engine that's "too complex" to mod. If you've ever been around anyone from the mod community, or participated in the community yourself, you'll know how dedicated modders are, and just how phenomenally good many of them are at what they do, almost to the point of being as good or in some cases maybe even better than the professionals in some aspects of game design with the mods they create.
You make a valid point Dirty Hipster, modders can overcome just about anything when it comes to "their baby" as it were, like the guy who made UnWheal a racing game using the Unreal engine, it caught Epic games completely by surprise.
But as technology gets more complex so to does building game engines, more and more developers are having to license third party software to put into their own game engines, these are the parts they can't give out to the modding community, because they don't own it hence they would have to rip it out.
Does that make sense?, sorry my brains in multilingual mode.
Back in 2001 I think Warren Spector envisioned the future of game developing as one company creating characters, another creating the physics, another creating the dialogue.. so on and so forth
As an example, I'm pretty sure Frostbite 2 uses Maya, which DICE do not own the rights too.
edit: I believe I got NINJOWNED!