In the 90s I used 3 different desktop OSes where the UI followed a style guide, and that style guide evolved gradually over years, allowing you to glance at a control and be familiar with its possibilities. Now even on one device, the user sees 10 kinds of different controls and new ones that are thrown at them all the time. The problem is surely that you can't rely on the user _recognising_ the control you've built. You have to design as if every user might be parsing it for the first time.