Rail really starts to shine when you've exhausted a few ore patches and it's much more relevant on railworld generations where you have large gaps of mostly nothingness.
It is about expansion. All you need to do to get that copper patch is extend the network from your nearby coal patch and build a station. Whereas you might need many thousands of belts to do the same and you wouldn't be able to share the existing infrastructure of the coal patch (unless you really like sushi as well as spaghetti).
I've really embraced the main bus for my playthrough and thus far it's done wonders for keeping everything neat and orderly. My only complaint is that it's stating to get annoyingly chunky and splitting off the bottom lanes burns though like half a stack of yellow underground belts, but at this point that's the more of a problem for the construction bots.