On an iPhone, for example, the appointment with the phone number and PIN means you can’t dial automatically. So you end up writing down both numbers and reverting to the keypad.
How that remains a shortcoming overlooked by Apple software engineers I can’t say. But it’s annoying as hell. Plus cell phones on headsets, so you can have your hands free, don’t duplex. You can drone on while someone else is talking, or vice versa, and you can’t tell. Once people catch on, no one knows when to talk or stop talking. Awkward! Then there are cell phones in vehicles, where the rush of wind from the open sunroof drowns out the whole call for everyone.