Because your point seems to be "if someone can draw and code, let them draw and code". My point is "if everyone focuses on what they are most good at, the end result will be better" and "if you can draw and code, and don't want someone else being able to tell you what you can and can't do... make the game yourself. You can draw and code, so nothing is preventing you from making your own game no one else can govern."
And that's exactly what I do. I have been driven by the attitudes of other developers into doing everything myself. I tried working with programmers before I could do it myself, and it's honestly frustrating not being able to do certain things because you don't have access to something trivial. I'm NOT saying give them the entire source. However, if there's a certain method needed for... let's say projectiles, then artists should be able to use that in order to test how they look. There are small things that being able to do on either side is wildly convenient. The artist shouldn't have to WAIT for you to implement it, test it after you compile and run it, then tweak it, then test again, then tweak again if needed. It's stupid to have to wait on other people to do that kind of thing.
My point is not "if they can code, then you have to let them code". My point is if they can code, then they should be allowed to utilize that to help keep things cohesive within the project. If the above projectile method had to be done for an entire game with tons of projectiles then it only makes sense to let the artists do that themselves.
Once again, this requires SOME code, not the entire source.
I'm in agreement with ATHK here. I work as a sort of hybrid artist/programmer, and the way I work absolutely requires me to have access to both the entire source code, and the entire list of art assets.
Why? Because the way I implement systems requires the art to be organized in the DMI files in a particular way. I shouldn't have to explain to the artists that the shields need to be split into under and over states, I shouldn't have to explain to an artist that the arrow stick glitz effects need to be positioned in a particular manner.
I give the artist a job, and I expect them to give it to me in a sprite sheet, that I later import and process myself. I give the environment artists a job, and they don't need the source code of the project, just prototype stubbs and an understanding of what types of objects need to go where, and when something needs to be a /turf/blockage and when something needs to be a /turf/elevationchange.
In the end, I don't like paying my artists more than I have to, so I want to make sure we have a clear outlined goal of what needs doing, what assets need generated, and exactly the sort of style and overall goal I expect. However, I'm also working with an artist. If I am paying them to put lines on paper, I'm also going to be paying them to be creative. If they can't read my "fluff" outline, and look at my base concept sketches and improve them with the final product? I don't want to work with them. If they can't keep the palette rules in mind, and can't avoid using 300 colors in a single gradient, I don't want to work with them. If they can't keep my explicit size/scale rules in mind, I don't want to work with them.
However, there is always room for creativity, and I will always gladly welcome asking why, as well as attempting to experiment a bit with an effect that just looks cool. But at the end of the day, if I'm giving my artists SVN access and expecting them to implement their own animations and whatnot into the right object prototypes, and expecting them to set up the animations properly, there's something seriously wrong with my priorities.