When applications evolve based on the demands of users, they tend to take a bad turn.
Features used by only 10 percent of users, or used only 10 percent of the time, are added and get in the way of the remaining 90 percent of features. They clutter an otherwise clean interface. They interfere with the features used most often.
And when "featuritis" takes over, you quickly find yourself permanently providing tech support for things that shouldn't be in the tool to begin with, fixing more bugs, writing more help material, and neglecting other, more important features. And while this may sound like a lot of fun to certain (slightly crazy) programmers, it's clearly the wrong approach.
The focus should not be on features, the focus should be on focus. An obvious application is a focused application. It's easy to explain to other people. It makes sense to those using it because the purpose of the tool is self-evident, and nothing in it strays from that purpose. Every feature supports the single activity the application is designed to support.