There is no single purpose that all artists pursue when they create a painting. In fact, the purpose of painting depends on the particular person doing it. However, there are some reasons that are more common among people than others.
For example, many people paint in order to convey a particular feeling. Such people often want to push the viewer towards a particular feeling or perspective. Another reason for painting includes trying to achieve fame or fortune as a painter. Painters might also want to record historical events as they happen, and they document these through paintings. Finally, painters might want to educate the audience through the items that they paint.