Why would an artist choose to use harmony i n a piece of art work

It can be used to stimulate and provoke. But it is mostly used to create pleasure at some level and to speak to our appreciation of color, light and texture, line, movement, balance, etc. In this painting, the artist first used a warm under-painting to establish basic harmony between the layers

because of the importance of consistency in data collection. but we have to evaluate the resource or information, and not just accept what is posted online since information available on the internet is not regulated for quality or accuracy.