Is it ok for Ola/Uber drivers to ask you to pay outside the app?

This happens so often and I generally refuse cause it feels unethical but I was wondering if the ride sharing apps are squeezing them tight so they have to resort to such practices to make money. And if for whatever reason they insist and I have no other option, I always pay less than what the app shows since they are trying to take the commission of the ride aggregator as well. I mean they can’t deny the fact that without the aggregator, they wouldn’t have found the customer in the first place. But today a driver was trying to guilt trip me into paying the full amount that the app was showing cause he felt he isn’t getting a fair amount. And I’m not sure what the right thing to do here is. I feel like if I pay the full amount then I’m encouraging an unethical practice. What are your thoughts on this?