I'm not sure that it's just funding. Collecting fares also creates capitalist incentives which is ultimately good for an end user, since the transit system is incentivized to do things (increase frequencies during rush hour, create more reliable systems) in order to collect additional fare revenue.

You could argue that it's all "just funding," but fares can help to prioritize work which will help collect the most future fares, creating the largest positive impact for end users.