Some artists surely can't spend much time on a single picture ; people doing a comic or keeping some Ask blogs, for example. Also there's probably a balance. We all saw works of moderate complexity getting all the upvotes and some very detailed sceneries getting unnoticed ; the theme of the picture is still the most important thing. If an artist is successful while keeping a simple, light style, why bothering with more work?Another reason is that a badly done realistic lighting will usually look worse than a simple one or none at all, and lighting is just hard. One can imagine few people will want to pull all the effort to reach an acceptable levelShydale seems to be among the few who have found a way to make great pictures efficiently. He doesn't have all the unnecessary complexity and complex, useless background/details etc, it's really inspiring.