I didn’t used to tip Uber drivers in cash. Much of the value add of the platform was its seamlessness. Tap a button, there’s your ride get in get out. No messy transaction to deal with. I even have to remind myself to pay when taking a taxi.
In-app tipping is far better than cash, anyway, it’s more convenient for riders and you avoid the problem of scantily clad women stealing Uber driver tips.