Onur Cobanli explains:
Many people say a variant of this, a few write it down, but no one say why this is the case so I dare explain; when you have simplicity, you have less elements; less variables, with less elements and variables you can optimize your design better because you have less permutations to explore and less number of iterations to make to arrive at perfection, for me that's one reason why simple is good; then there is the cost perspective, simple costs less; less number of materials or parts will mean less production or realization costs, this is good design, and finally there is the third reason; and it is about ease of understanding; it is easy to understand simple things, it is easier to use simpler products; there is a different type of benefit in this too, this does not of course undervalue designs and products that need to be complex in their nature; somethings cannot be simple, but when it can be, it should be. Modern design is generally simple because it is expensive to make complex designs in the modern times; expensive is usually not good design; it implies inefficiency, efficient design is good, efficient design is usually simple.