That is refuted by the diversification of today's most valuable companies: tech firms that have branched out into driverless cars, cloud computing and so on.
Your UI tests can now branch out into many other apps, which is a great improvement for working with app extensions, settings, and other integrated work flows.
The arteries branch out into narrower and narrower arteries, and then arterioles, and finally gets to the capillaries - which have walls that are only one cell thick and are slightly porous.