Consider the following regarding NY, DC & SF subway systems:
"How Politics and Bad Decisions Starved New York’s Subways Disruptions and delays have roiled the system this year. But the crisis was long in the making, fueled by a litany of errors, a Times investigation shows." 2017 https://www.nytimes.com/2017/11/18/nyregion/new-york-subway-...
"Metro sank into crisis despite decades of warnings Metro’s failure-prone subway — once considered a transportation jewel — is mired in disrepair because the transit agency neglected to heed warnings that its aging equipment and poor safety culture would someday lead to chronic breakdowns and calamities." 2016 https://www.washingtonpost.com/local/trafficandcommuting/met...
"Past decisions haunt BART as it seeks voter OK for $3.5 billion bond" https://www.sfchronicle.com/bayarea/article/Why-BART-s-futur...
Sending the capital to maintenance would be a politically driven project right now for public utility. For private company even right now it is still a conflict of interests between maintenance and shareholder interests.