Well, I agree that a game shouldn't look bad, but a developer (especially one who is using 3DGS) shouldn't sacrifice a part of the potential buyers by implementing shaders. It is alright with me, if a game uses such techniques that work on most of the video cards and still looks good. That's just great!!
But the difference between other games that use shaders and 3DGS games, I guess is the possibility to have fallback options, as others mentioned here. Well, here's a question - how hard would it be to implement shaders in a 3DGS game, but also have these fallback options, that somehow fake the shader? If that is possible with 3DGS and not very hard, then I'll stop ranting here! ^^

Leonardo