Lightspark’s chief design officer Geoff Teehan, writing in Design Field Notes, traces the work that comes with adding a UI control:

By details, I don’t just mean the small visual decisions. Every feature, control, mode, state, exception, and bit of behavior becomes something a team has to design and someone has to understand. There’s only so much attention to go around. Same for time, taste, and patience.

A button seems harmless enough, but someone has to decide where it goes, what it says, what it looks like, what happens when you press it, what happens when you can’t, and what happens after you do. Add another and now you don’t just have two buttons. You have the relationship between them.

Teehan’s examples distinguish reducing that work from simply hiding controls. Teenage Engineering’s gorgeous OP-1 combines a synthesizer, sampler, sequencer, recorder, and mixer. It still takes practice to use. But its four colored knobs correspond to colors on the screen, giving the musician a consistent way to make adjustments across different functions. The colors do a job here. Removing them to make the instrument look simpler would undermine the relationship Teehan describes.

He closes with what a team can do when it has fewer details to maintain:

Removing something gives you time back. Time to reconsider the typography, rewrite three words, make an interaction feel right, move something two pixels, tune the sound, or notice what becomes annoying after the twentieth use.

Most people won’t notice any of it. Fine. They shouldn’t have to.

Minimalism isn’t the point. You can make something sparse and still make it bad. The goal isn’t to have the fewest things. It’s to have few enough things that you can care deeply about every one of them.