I'd argue it's easier to not tip when you have the option to tip in the App. If you're transacting with cash the driver knows if / when you aren't going to tip them. It'd be next level aggressive to sit and watch if you tip the driver on the app before you get out of the car. Personally, I'm fine to tip since the normal barrier to tipping for me is having cash, but either way in app tipping seems to make things easier.