I hate seeing that in a terrain, it totally ruins any suspension of disbelief. It is more lazy terrain design than a problem with the terrain.
When building a terrain the designer hits a button in the editor and it builds all the roads and railway lines with their trains and trucks for all the fields automatically. The problem is the editor just lays all these out heading due north from each field. The designer can then reroute the roads around hills and lakes by hand if he chooses to or replace them with barges. With up to 255 fields plus strat objects needing supply routes on an MA map this can be a right time consuming PITA.
It would be nice if HTC could make the automatic road laying routine in the TE a bit more intelligent, so it lays them out avoiding steep slopes, water or another road. This would save a lot of time on building a good looking MA terrain.