Simplicity is costly. You have to give up something to achieve it. You can’t just add it on top. William Bridges illustrates this in his book The Way of Transition where he describes his moving out to the country.
… I had been infatuated with Thoreau’s Walden and its story of living a basic life, close to nature. The heart of that undertaking, he had written, was to simplify your life. … In retrospect, I can see that although I thought that this was what I was doing, I was really just trying to add simplicity to my life. In addition to all the old things I had been doing … Of course, my life grew more and more complicated in the process.
A simplification has to remove or replace something else. You can’t just add on simplicity.
There may be an exception to this. Sometimes you can add a few missing pieces to make something more symmetric. In that case, the additions simplify the whole. (Mendeleev did something like this when he drew his periodic table.) Even then, I suppose you could say you’re removing the asymmetry. In any case, achieving simplicity usually requires more subtraction than addition.