Having darker lines will give more reasons to add per pixel lighting to replace our currently crappy vertex lighting in the next update. Dark lines on bricks and tile prints by default and better lighting will allow people to make better horror builds etc. These shadows are going to help a lot too. I can allready imagine myself making dark caves with it.
EDIT:
It's funny because this is 100% true. If a build doesn't have lights, and you load it in a map like Destruct, it's very hard to find that build.
It is your choice to download these dark maps, because there are currently no maps that are in complete darkness (the darkest being bedroom dark and kitchen dark, which will be removed in the next update). Besides, we have a good selection of lights that we can use, including the many useful light add-ons.