I can't really think of any that don't already exist or are just based on not wanting to share spaces with poor people, but I'm open to listening.

We don’t just want to maintain the current levels of service and ridership, we want both to grow, ideally a lot. So even if you could replace the current fare revenue with taxes—which is already not gonna be easy—you’d be facing an uphill battle every time you need more money to expand service.

The great thing about fares is that they automatically scale with ridership, so agencies can borrow money for expansions knowing the resulting increase in fares will allow them to pay it off, and not be at the mercy of voters all the time.

Wouldn't taxes provide a more steady revenue stream?

Steady, yes, but the trouble is it doesn’t automatically scale with ridership, so every time you want to expand service you need to raise taxes, which will always be an uphill battle.

None of this is a downside, just challenges of implementation.

If you want ridership to grow by a lot then free fare is a great way to do so. I know I'd ride the bus a ton more.

That will increase ridership up until the point where you reach the limit of the existing infrastructure, or you exhaust the supply of price-sensitive riders. After that, the only way to continue increasing ridership is to expand service, which requires money.

Yes. Is that a point you're trying to make? That things cost money?

The point I’m trying to make is that there are downsides to making transit free, maybe the pros still outweigh the cons, but it’s not simple and there are certainly reasons not to besides “not wanting to be around poor people”.

It's incredibly simple. The only "downside" is that we pay for it through taxes instead of at point of service.

And I have spent several posts explaining that there are important functional differences between paying at the point of service and through taxes. I guess you aren’t open to listening after all.

I hear what you're saying. I don't agree that it functions as a downside as you said. Especially when compared to the upside, both financially, and in quality of use.