After a long break from Uber I opened it up to price compare against Lyft. I switched between the two apps and then uber offered me two free rides. It seemed like it was detecting that I was hesitating to "come back" to Uber.

I use Android Lollipop and even if the permission didn't allow them to see I was using Lyft, I wouldn't be suprised if they're trying to re-engage "hesitating" users and are snooping for whatever data they can.