Yeah if you cherry pick a long journey that's possible to do in one go on the tube you can obviously find situations where public transport is cheaper. Most of the time it is. But there also exist journeys for which Uber is faster and cheaper, especially with two or more people, and especially at night.

Or journeys where Uber is marginally more expensive but people are willing to pay £1 for convenience.

I'm not sure what we're arguing about, the fact that it's 40k drivers and the everybody's phones just received several messages about it proves that there's demand.