"the model seemed to be based on a high-turnover of drivers and another sucker along in a minute."
This is the entire basis in the recent "gig economy" phenomenon. Things like Uber and Airbnb started off as a nice sounding idea - if you happen to have an empty house for a weekend or are driving somewhere, why not make a few quid by letting someone pay you for letting them share? And while even that runs in to a variety of legal issues that most people just choose to ignore, in pure financial terms it really isn't a bad idea; if I'm driving anyway, giving someone a lift doesn't add significant extra cost so any pay is pure profit.
The problem quickly turns up when people try doing it as an actual job instead. At which point they quickly discover why they weren't already raking in the money running a taxi or hotel business to start with. Even if you still try to ignore all the legal issues like licensing and insurance (which isn't going particularly well for Uber and others), it turns out running a taxi service is a lot more expensive than most people think. Hence all the people jumping in, failing to make minimum wage, and then having to drop out again because it doesn't actually pay the bills. Normally this would be followed by "...but of course the enabling company always makes a profit by taking a cut", but in most cases even they haven't figured out how to actually make any money out of all this.
It's all a bit weird, because the idea of casual labour is hardly a new one, and the way Uber assigns work is not meaningfully different from the way manual labourers used to be picked up for working on the docks, and a lot of casual and manual work is still done in similar ways. But for some reason put an app between the hirers and the workers and suddenly everyone involved loses their minds and thinks a magic money tree has appeared somewhere in the process.