Uber is actively developing ride experiences like UberPool and UberHop that link multiple riders together in ways that can avoid a driver's car ever being empty. If the car isn't empty, they can't turn on Lyft.
Lyft Line does the same. As far as cars not being empty, during non-peak hours the streets of San Francisco are filled with Uber cars driving around with no passengers. I guess Uber Eats or whatever is supposed to fix this. No passenger? Stick a salad in the passenger seat.