Final answer:
Amtrak's limited spread in the US is a result of the rise of automobile travel, competitive and efficient air travel, and constrained funding and political support for rail infrastructure compared to air and road systems.
Step-by-step explanation:
The reason why Amtrak doesn't go to more locations in the US mainly revolves around the decline in passenger rail travel due to the rise of automobiles, the growth of a competitive airline industry, and insufficient funding for railway infrastructure. After recognizing the need to maintain a passenger rail service despite dwindling profits, the US government consolidated the remaining train lines into Amtrak in 1971. However, deregulation in the airline industry led to reduced airfares, more efficient aircraft utilization, and the hub-and-spoke system which made air travel more accessible and convenient compared to train travel, thus increasing the prevalence of commercial air transport. Additionally, constructing and maintaining rail lines requires significant government oversight and investment, which has been limited in comparison to the development of civil airline infrastructure. As a result, rail lines did not expand at the same rate as highways and airports, which receive more funding and policy support for growth.