I mean, it’s essentially just the metro… but above ground. Except that above ground location is out of the way of existing ground-layer infrastructure like sidewalks and roads.

In essence, it’s just the benefits of a metro line with the added benefit of taking up less space from existing areas that can be used for transport. If you already have roads, sidewalks, and metro lines in an area, a monorail can just be another way to get around on top of all that without sacrificing space.

I’m not saying it’s perfect, but it’s a cool mode of transit, and can be genuinely useful in some cases.