But it's niche. Its amusement parks and tourist rides. One or two tiny systems and I think a reasonable sized on ein India. But its hardly the future transport the 60/70s promised it would be.
The systems I mentioned exclude tourist rides and are real urban rapid transit systems used every day as such by residents. I don't think many of these really could be considered "tiny" in the way that the Seattle monorail is - these systems are larger than many cities' proper heavy rail metro systems. They certainly are niche, but monorail (and maglev, and now hyperloop) have always been intended as niche products for very specific circumstances, that they may or may not ultimately excel at. No one seriously proposed replacing a national heavy freight rail network with concrete beam monorail, just as Elon Musk isn't trying to get BNSF or UP to haul coal across country in hyperloops. If anyone in the 60s was actually proposing that monorail was somehow the future for all types of rail haulage they were either an overeager Alweg salesperson or a SciFi writer who didn't fully grasp the concept. Hitachi's monorail division seems to be doing just fine in terms of sales, even if Hitachi makes much more in revenue from heavy rail. Monorail (and other light rubber tired systems) can be built elevated less obtrusively that heavy rail, and can handle steeper inclines. For some lines these criteria may be more crucial than through running with a national network or more familiar equipment.
Beyond monorail and hyperloop, there are plenty of other small guided transit concepts that have no way of interfacing with either road or standard gauge rail, yet are still successful without becoming ubiquitous; primarily rubber tired metros and people movers, but also even various steel on steel rail systems, whether they be narrow gauge or light rail. Even large standard gauge heavy rail metros often have no real connections to the wider rail network and new vehicles are delivered by ship or truck rather than rail.
So Erm. Yeah. Any examples?