a) you could never "hail" a mini cab in London, only a black cab. Uber effectively allows you to hail from your phone, changing the market conditions
b) Drivers getting 80% is all very well but they can't plan their shifts all the time can they so it's 80% of a moving target
c) Even if Uber are not in profit their VC backers will be and they will be avoiding tax as much as possible - though granted that's capitalism in general for you and I'd rather have that than Brand's socialism.
a) We weren't just talking about London, but 'calling' a Uber by pressing a button on your phone is just an easier way of calling a minicab using your phone (and your voice).
b) No idea what you're saying.
c) VCs lose out on plenty of businesses they invest in that bomb. Now and again they strike a unicorn like Uber. Sometimes they miss striking gold too. Regardless are we now trying to figure out if VCs pay tax on their investments?