1. In nearly all of the US (maybe everywhere except parts of NYC?) it is a worse experience than driving (requires planning, takes longer, can't carry more than one or two bags with you).
2. It is déclassé.
I think #2 is at least partly a result of #1. Also note that #1 is true even for most cities in the US, because cities in the US are unbelievably car friendly compared to cities in e.g. western Europe. I don't see any public-transit solution that doesn't involve intentionally making the car experience worse, and that's going to be a tough sell to voters.