Ride-share companies are losing billions, so why their interest in unprofitable public transport?

Why do Uber, Lyft, Didi, OLA and other ride-sharing companies want to partner with public transport agencies? For Uber and Lyft, the reason is simple: their business plans were based on eventually using driverless vehicles to eliminate their main cost, the labor cost of the driver. But human drivers won't be replaced for some time.