>>1985872I don't think they were ever considered futuristic. The idea has been around since the early 1900s or possibly even before, but it was always obvious that the technology sort of sucks for anything beyond a few niche applications. They never took off as a practical form of *mass* transportation because with single track rail, switching becomes a lot more complicated and annoying to figure out. However, that's also why they did work in some applications where they only needed a single track with most switching just being to go into maintenance or storage sidings. They really just don't have any purpose when normal rail exists, so they never took off. Why use a monorail when 2 rails works and is superior?
Airports and amusement parks sometimes have them and they work there. A few world expositions did too - pic related, it's the one Brisbane, Australia in 1988. These are usually temporary though. Okinawa and Chongqing are examples of cities with pretty complex monorail systems, but they're also simple in terms of the route they take.
Tl;dr they don't really serve a purpose when regular rail does the exact same thing. Maybe the only extremely unique use cases would be like...underground mining or similar operations, where suspending rails is easier.
