They're hugely successful in London, so pretty well I guess?

Are they? First time I'm hearing about those. Is there actual demand for this?

I live in their target area and I can't ever recall a time where I wanted to combine the risks & downsides of biking and ordering a cab.

If I want to bike (note: I wouldn't recommend it in Central London), I'd get the Santander bikes or the various bike-for-hire ones littering the streets and just do it myself.

If I wanted to spend time fiddling with my phone, I may as well just order an Uber instead of this thing? The prices would be similar considering they both have to pay drivers and driver wages represent a significant chunk of the sticker price of any manned transport-for-hire service so I really don't see why anyone would get this thing instead of a good old Uber.

I see at least one or two of them every time I commute across London, they seem predominantly used for transporting items rather than people.