The automobile led to the demise of our railroads. Even today a lot of freight travels on trucks when it seems it'd be more practical to ship it on trains. Most likely the majority of our populace would prefer to travel in their own car rather than take a train to a destination I think having our own wheels with us leads to a lot of that thinking, along with no hassles renting a car.
Reduced availability of trains has led to higher prices to ride the ones that do run. Although much less comfortable and much more hassle, air travel meets more peoples' needs: rapid transit. The days of riding and seeing the country are behind us. Today everyone wants to get there quickly, do what they're there for, and get home quickly.
As a kid, I remember a couple train trips to Missouri to visit relatives. Would love to do that trip again, but the nearest passenger depot is over 300 miles...totally impractical.
Philadelphia has good rail systems. Trolleys go around to a lot of outlying neighborhoods, commuters can take the train into the city to work, and you can get a long distance train at the same terminal. Besides that, they have good bus systems, too.
I used the combined bus and trolley system to get to work, enjoyed it immensely. While you are waiting for your trolley, you can grab a good bagel and cream cheese or a cheese-steak sandwich.