Where I live, all too often there just isn't any runway to do this. When you're trying to merge, say, here: https://binged.it/2DTnemt then all you can really do is rip right into traffic and people will just have to make space. It's the worst possible layout for supporting a smooth traffic flow, and it baffles me that they don't lay the extra 200ft of asphalt to improve this, especially in a state that has a DOT that does know how to apply innovative solutions to increase traffic flow like SPUIs and CFIs.