I believe that most developed countries understand that the arts are necessary for a country to have as a form of education, entertainment, profit and to signify who they are or were as a people. Additionally ticket sales from plays, movies and exhibitions can offer large financial returns if they are successful.
The economics of a country, in most cases. support art subsidies. A society without art is, at best, a second world country. The government contributing to art is contributing to a society that sees things the same way. While one artist might not unite all of the subjects of the country in a universal belief, sponsoring many artists can create many chances for different segments of society to connect and grow with one another based on similarity in art tastes.