"hey are truly disruptive because they make use of otherwise...

"hey are truly disruptive because they make use of otherwise idle assets and are therefore a marginal cost player, whereas CAB is a total cost player. - they cant win."

I'm a believer in "sweating assets". From a productivity perspective - asset utilisation alone does not represent an opportunity for the marginal cost player.

We need to consider other factors such as insurance, lack of regulation, willingness of customers to take on risk - transport timing or safety, etc.

While I can mostly relate to your line of thinking - I struggle to convince myself Uber signalling the end of taxi services. This is not a more convenient way to purchase/sell books. This is a time critical function that people will interact with frequently and at a personal level.