Monorails lack flexibility and are not really suitable for anything beyond short loop routes. Plus, you're married to the technology of whoever builds the system. Not everyone can build a monorail, yet many manufacturers can make equipment that runs on two rails.

Monorails are often viewed as futuristic, but they remain unpopular for mainstream transit due to high costs and technical limitations. Unlike standard rail, monorails require a continuous, specialized concrete or steel guideway, effectively making the entire route a "bridge that never ends." This massive infrastructure is expensive to build and visually intrusive in urban areas. Operationally, monorails struggle with "switching"—moving a train from one track to another requires heavy, slow-moving beam sections, making complex networks difficult. Maintenance is also a hurdle, as elevated tracks are harder to access than ground-level rails. Furthermore, the proprietary nature of monorail technology means cities are often tied to a single manufacturer for parts and cars. For these reasons, while they excel in specialized roles like airports or theme parks (where grade separation is a priority), most cities prefer light rail or subways, which utilize "off-the-shelf" technology that is cheaper to install, easier to expand, and offers higher passenger capacity for less investment.