It might be enough to get someone to try transit and see that it actually does work. If you are used to driving everywhere and have never used transit then you won't actually know how it works. Routes, timing, transfers, missing the bus... - there are a lot of things that are different about using transit, none of it hard, but all of it needs to be learned. Free transit may be enough to get you to try it once (exactly once!), and if transit works that will be enough that you become willing to figure out how to buy the fare in the future.

In general free transit is a bad idea - nearly everybody is willing to pay a small fee for transit and what they really want is better service (better service meaning more routes, faster routes, and more frequent - pick as many as possible)