The interaction surface usually is just tip of the iceberg.

Here's a thread [0] regarding the complexity of Uber's iOS app.

Dan Luu made a far better case [1][2] for this than I could. Worth the read.

0: https://threadreaderapp.com/thread/1336890442768547845.html

1: http://danluu.com/sounds-easy/

2: https://twitter.com/danluu/status/782974159156502534?lang=en