Motivate is behind Citi Bike in New York and Ford GoBike in San Francisco, along with bike-sharing programs in other cities including Boston, Chicago, and Washington, DC. Commuters used its bikes 3.18 million times last month.

As the battlegrounds get more intense for the companies' non-ridesharing offerings, Uber and Lyft are exploring electric scooters and, yes, bike sharing. Uber recently bought Jump, which has an exclusive permit to run a dockless bike share system in San Francisco, so Motivate would expand its portfolio of urban services.

Both Uber and Lyft have reportedly applied for licenses to run electric scooters in San Francisco; scooters were recently pulled from the city's streets pending a licensing process, in part because they've proven a nuisance for many. There are more ways than cars to get people around cities, and both companies seem to be focusing more on alternative transport methods. Bike sharing, at the very least, would be a stopgap until flying cabs come along.