Trains are not so bad. A major problem is the lack of a local area support network of public transport.
Example: there is a train from Los Angeles Union Station to San Diego. But how can one go to LA Union Station? From Santa Monica, Venice Beach, West LA, Pacific Palisades, etc. it's just plan impossible. The Metro bus is a joke: it takes over an hour, and likely you need a previous bus with added waiting times in between (and buses are unreliable because they have no exclusive lanes to avoid heavy traffic). A taxi is very expensive ($60+). You need a friend to drive you there. And once in San Diego the situation repeats itself.
Same situation, but a bit less bad, in the East Coast: nice trains from Washington DC to NY and Boston. While Boston and NY have very decent local transport systems, Washington's doesn't really go anywhere. Again one is stuck with $60+ taxis to go anywhere.
Example: there is a train from Los Angeles Union Station to San Diego. But how can one go to LA Union Station? From Santa Monica, Venice Beach, West LA, Pacific Palisades, etc. it's just plan impossible. The Metro bus is a joke: it takes over an hour, and likely you need a previous bus with added waiting times in between (and buses are unreliable because they have no exclusive lanes to avoid heavy traffic). A taxi is very expensive ($60+). You need a friend to drive you there. And once in San Diego the situation repeats itself.
Same situation, but a bit less bad, in the East Coast: nice trains from Washington DC to NY and Boston. While Boston and NY have very decent local transport systems, Washington's doesn't really go anywhere. Again one is stuck with $60+ taxis to go anywhere.