Uber and Lyft are NOT transit

TNC are  not mass transit; it's a taxi. (There is no massification)

Shared ride _is_ transit. It's a jitney. Jitneys also follow routes. 

The idea that you can combine the 'on-demand' dial-a-ride of a taxi with a jitney is fallacious.

How much detour are you willing to tolerate? And when does it make sense to stop and add another person.

Massification relies not only on spatial convergence, but also temporal convergence: 

Same people in the same place at the same time. 

Which implies it will mostly take place during times of peak demand. 

Which becomes the classic transit agency problems: Sufficient peak capacity is excess off-peak capacity.

The real innovation of TNC's is not the 'dial-a-ride'. It's the ability to use 'surge' pricing to manage the match between supply and demand. It both reduces demand (through higher prices) and draws in additional drivers (through higher fares). 

This is core to the whole TNC model, as it draws in latent supply.

'Latent supply' is how the whole TNC thing works. Most cars are parked most of the time.

Commuting in the morning, the commute+shopping in the evening.