They are scaling back. I suspect that they are trying to accomplish several things with this.
Initially, they wanted to get more drivers on the street. Uber knows quite well that the rates are too low and that drivers are starting to quit more quickly than their replacements can be onboarded (or at least as quickly or something approaching that). How do you get out more drivers? Simple: offer them more money.
Uber needs to see what is the lowest figure that will keep out there an adequate supply of drivers. This is why it keeps cutting back on the incentives. At some point, Uber is going to have to increase the fares. Obviously, it wants to keep that increase to a minimum. See what the drivers will take, drop that figure by a little bit more, there is your fare increase.
Uber is trying to squeeze Lyft. That seems to be working. I have been trying to get a Lyft ping all week, especially when Uber sent me to stand in the Virtual Corner. Further, I do want to keep the Lyft account active, so I do need to cover a ping here and there. I could not get one. Finally, to-day, I got one. I had to let expire two Lyft Lines, but finally, I got a regular Lyft. I am guessing that people are using Lyft less because there are no drivers available; they are all on Uber taking its money.