I think the issue here is just the 'size of solution' between private and public transport offerings. i.e. If you've got tens of thousands of people in a place

I think the issue here is just the 'size of solution' between private and public transport offerings. i.e. If you've got tens of thousands of people in a place - an underground line isn't a bad idea. If you've got tens - then that's not even enough for a bus. However an Uber driver (or even a pool route) is actually happier with the latter, as they're not having to compete with an underground. Different types of transport tend to be poorly integrated. Maybe airports being the only example I can think of where private and public play nicely together.