Onur Cobanli explains:
In general, the design process is about improving things, making products better, and services superior. Testing product variants or service differences, i.e. iterating, is very important for making better designs; you test variants, you try new things, keep good and discard bad; iteration is the soul of design process; it is optimization and it is essential, obviously if you do not iterate, you settle for mediocre; regardless of how great your design is, if you iterate, you may potentially arrive at even greater designs.