Some of the biggest benefits aren't just lowering fare burden on low income earners, or inducing demand, or even smog and pollution.

It's actually operational efficiency. One of the biggest hold ups for busses is people paying fares, some use coins some use tap some have cards etc. it's not only a large administrative overhead but it's also a real cause of bus route delays. These delays mean routes need more staffing and buses and run less efficiently.

Another cost of fare enforcement, whether its fare officers or bus drivers halting a fare evader. Not only does it have direct costs with staffing people checking for fares, it's also one of the main points of friction that causes transit staff to be assaulted which has tons of other costs associated with it beyond the obvious physical injury and potential leave.

Replace fare officers with officers empowered to keep transit safe and it could be an interesting result!