For other purposes, not.
You've hit the nail on the head there, as to why tools like these are good for some purposes but not for others. If a task has directional asymmetry (where there are anisotropic effects based on directionality) these tools are probably not the best choice and a vector approach would probably be better.
I think raster tools, like GRASS, were more popular in earlier years because raster data was much easier to acquire for regions of interest. One pass with a radar scanner on a satellite and you get a whole region full of terrain elevation data - much easier than going out into the field and measuring a million locations point-by-point in the days before GPS, or before computed extraction of terrain heights from multi-angle aerial photography. Vector GIS tools were also very feeble, with very poor DBMS capability to handle attributes in the modern way.
But raster oriented tools, like ESRI's Distance tools and Manifold's Closest tools, are great for applications where data is raster in nature, and mostly continuous and isotropic. Take slopes as an example. Some applications using slopes don't really care about directionality, while others do. Your example routing electricity lines is a don't care example. Other examples are routing oil pipelines, where it's much more costly to run oil pipelines through terrain with lots of up and down slopes than it is through flat terrain.
Migration paths of people and animals are another. The up and down slopes in rough terrain, like the Appalachian chain of ridges (see this image) , average out in terms of "easy going down" / "hard going up" but the result is a higher "cost" going across the ridges than following the valleys. If you want to see how animals migrate through such terrain, or the paths along which earlier civilizations were linked, doing Path analyses using slope will provide insight.
It's true raster tools won't help much doing optimized routing in cases where vector tools are a better choice. A good example might be walking routes for tourism in our beloved Hong Kong, the topography of which features a high mountain ridge overlooking the densely populated strip of neighborhoods below. Many of the interesting neighborhoods are on steep slopes. To facilitate uphill travel, Hong Kong has a superb series of outdoor escalators to take you uphill without effort.
The key to least cost walking tourism is to take the Central / Mid Levels escalators up and to then take serpentine walking routes down through interesting neighborhoods. You take the effortless ride up and then it's an easy walk down.
But planning your tourist route using directionally symmetric raster paths isn't going to work. You need a vector map with one-way routes that have different costs depending on direction, so you can solve the graph problem through a directionally asymmetric network.
Conversely, trying that approach to understanding migration paths through terrain like this isn't realistic, not least because building a vector model over all possible routes is not so easy, and then doing geometrically more complex calculations for routing is also not so easy. A path solution for the entire terrain at once is a better approach, and that explains why people pay thousands of dollars per year to get such tools with ESRI. The ESRI literature I think would be worth reading for more examples of uses cases.