So just to expand on this, two things.
1) The build road to feature was found to be responsible for some crash or was otherwise broken/disabled. Whichever case, I believe there is no active plan to bring it back.
2) The route planner mod actually has a feature where it explains why roads have been built according to 3 categories so
View attachment 734091
Main routes were built to connect Cities. Shortcut routes are built to connect different areas but aren't strictly necessary to connect Cities (and I believe this does take into account maintenance). Strategic routes are built to Forts/Citadels, and along borders where they will be used in the event of war (and I'm not sure how much they care about maintenance here).
Perhaps
@KungCheops or
@L. Vern can elaborate, or point to somewhere else it is explained, if it has been.