Why was relationship between railroads and amusement parks?

Ruby describes her husband's motivation to build Ruby Park in the first place: "...[Emile] made a deal with a railroad company, which was looking for a way to increase its riders on the weekend." Eddie is well aware of this fact, thinking about how most people think "amusement parks [are] constructed by elves, built with candy canes. In fact, they were simply business opportunities for railroad companies, who erected them at the final stops of routes, so commuters would have a reason to ride on weekends"