Except, there are lots of reasons to subsidize subways, for example to encourage ridership which in effect can then decrease public roadway congestion. Thus, even the people who don't directly ride the subway still benefit. It also can reduce pollution as well has have local economic benefits. All of which benefits others, not just the riders.
This is only really true in cities where the major commuting pattern is into the city. In the DC area, for example, most jobs are in Virginia or Maryland, not DC. So the subway benefits the relatively small number of (disproportionately higher income) people who take the subway or a car downtown. It doesn’t really benefit all the folks driving to jobs in Virginia and Maryland.
Then allow people that care about roadway congestion or pollution help pay for it. No need to take money from people with better uses for it than cleaning your air or clearing up your traffic. ("You" being the hypothetical benefactor, not you the poster)
Source: https://www.apta.com/resources/statistics/Pages/transitstats... which gets its data from the Federal Transit Administration.