Why can we not drive our cars on to trains and travel from one city to another to save gas etc?

Question

You can go to Fl from Washington via a car train.

Answer 1

You can actually do that in major stations but you have to pay the daily parking fee.. In addition, there are local metro trains connecting to major Amtrak stations that has parking facilities so people can leave their cars there

Answer 2

Because the system is not in place. There is no enough parking, trains, etc. If they system was for the comfort of population it would be in place. like in Europe.