Not sure what you are arguing with exactly, theres a huge difference between commercial and commuter 'profitability'. Things that freely allow for commerce like a road can be justified from many different direction where a periodic service only makes sense based on demand. That isn't to say that maintaining an underutilized route with the goal of it becoming utilized based on is availability is always a bad idea, but a road can be built and it's cost can at least roughly be correlated to it's use. If you had to periodically rebuild every road, at roughly the same cost whether it was used or not, they would end up with the same 'profitability' concern, but mostly you have to build all the roads for minimal usability and then spend the most money on the most used roads. Freeways are understood to improve commercial visibility and are funded by taxes for that reason. The entire country benefits by having clear routes for good to move. Commuter rail primarily benefits a local area and is funded heavily by fares and local taxes.